Ako te zaboli ubod, odmah mi reci i sjest ćemo u hladovinu.

Because zaboljeti / zaboleti means to start hurting or to give a sudden pain, while boljeti means to hurt / to be painful more generally.

So:

• Ako te zaboli ubod = If the sting starts hurting / suddenly hurts
• Ako te boli ubod = If the sting hurts you / is hurting you

In this sentence, zaboli suggests a change: everything may be fine now, but if pain appears, say so immediately.

Also, zaboli is a perfective verb form, which is very common in Croatian after ako when talking about a future possible event.

Te is the unstressed accusative form of ti = you.

Here it means you as the person affected by the pain:

• ubod te zaboli = the sting hurts you

So te is the direct object of the verb.

Very often in Croatian, these short pronoun forms appear early in the sentence:

• Ako te zaboli...
• Ako me nazove...
• Ako ga vidiš...

Ubod literally means a sting, a prick, a puncture, or the act/result of being pierced.

Depending on context, it can refer to:

• an insect sting
• a needle prick
• a thorn prick
• the sting site itself

In this sentence, it most naturally means something like the sting or the place where you were stung.

So Ako te zaboli ubod is basically If the sting starts hurting.

Because ubod is the grammatical subject of zaboli.

The structure is basically:

• ubod = the thing causing the pain
• te = the person affected

So literally, the clause works like:

• If the sting hurts you

That is why:

• ubod stays in nominative
• te is accusative

This is a very common Croatian pattern with verbs of pain:

• Glava me boli = My head hurts / literally The head hurts me
• Zub ga boli = His tooth hurts
• Ako te ubod zaboli... = If the sting starts hurting you...

Yes, word order can vary, but not all versions sound equally natural.

Possible versions include:

• Ako te zaboli ubod...
• Ako te ubod zaboli...
• Ako ubod te zaboli...

The original Ako te zaboli ubod... sounds quite natural because Croatian often places short pronouns like te early, and the subject can come later.

A learner-friendly way to understand it is:

• te goes early because it is a clitic
• ubod can appear after the verb without changing the core meaning

So the sentence is not using a weird case; it is mostly a matter of Croatian word order.

Reci is the imperative singular of reći = to say / to tell.

Here it means:

• tell me
• say so
• let me know

So:

• odmah mi reci = tell me immediately

It is directed to one person. If you were speaking to more than one person, you would use:

• recite = plural / polite imperative

Mi is the unstressed dative form of ja = to me.

So:

• reci mi = tell me
• literally, say to me

In Croatian, this is the normal way to express tell someone:

• Reci mi istinu. = Tell me the truth.
• Javi mi. = Let me know.
• Objasni mi. = Explain it to me.

So odmah mi reci means tell me right away.

Because Croatian future tense is often formed with:

• the infinitive
• plus the auxiliary ću, ćeš, će, ćemo, ćete, će

With many verbs, when the infinitive comes before the auxiliary, the final -i of the infinitive drops in writing:

• sjesti + ćemo → sjest ćemo
• vidjeti + ćemo → vidjet ćemo
• uzeti + ću → uzet ću

So sjest ćemo means we will sit down.

If the auxiliary comes first, you usually keep the full infinitive:

• Ćemo sjesti
• Hoćemo sjesti

But in normal statements, sjest ćemo is the standard order here.

This is an aspect difference.

• sjesti = to sit down (perfective, one completed action)
• sjediti = to be sitting / to sit (imperfective, ongoing state)

So:

• sjest ćemo u hladovinu = we’ll sit down in the shade
• sjedit ćemo u hladovini = we’ll be sitting in the shade

In your sentence, the idea is let’s move and sit down there, so sjesti is the better choice.

Because u can take different cases depending on meaning:

• u + accusative = movement into/to
• u + locative = location in

So:

• sjest ćemo u hladovinu = we’ll sit down into / in the shade, meaning move to the shade
• sjedimo u hladovini = we are sitting in the shade

This is a very important Croatian pattern:

• Idem u kuću. = I’m going into the house.
• Ja sam u kući. = I’m in the house.

Here, the sentence implies movement to a shaded place, so hladovinu is accusative.

They are related, but not always identical.

• sjena = shadow
• hladovina = shade, especially a cool shaded place

In this sentence, hladovina is more natural because the idea is to sit somewhere cooler and protected from the sun.

So:

• sjesti u hladovinu = sit in the shade

That is a very common expression.

That is normal in Croatian.

After ako (if), Croatian very often uses a present form, especially with perfective verbs, even when English uses future meaning.

So:

• Ako te zaboli... = If it starts hurting you...
• Ako dođe... = If he/she comes...
• Ako nazove... = If he/she calls...

Croatian usually does not say the equivalent of if it will hurt in this kind of sentence.

So the structure is completely standard:

• Ako + present/perfective form
• then a future or imperative in the main clause

No, Croatian word order is flexible, though some versions sound more natural than others.

You could hear:

• odmah mi reci
• reci mi odmah
• mi odmah reci

The original odmah mi reci sounds very natural and emphasizes immediately.

Because mi is a short clitic form, it usually stays near the beginning of its phrase, while odmah can move around for emphasis.

Yes, it is natural and understandable.

It sounds like something someone might say after a bee sting, wasp sting, injection, or similar situation:

• Ako te zaboli ubod, odmah mi reci i sjest ćemo u hladovinu.

A very natural English rendering would be:

• If the sting starts hurting, tell me right away and we’ll sit in the shade.

Depending on context, some speakers might also say:

• Ako te ubod zaboli...
• Ako te mjesto uboda zaboli... = If the sting site starts hurting...

But the original sentence is perfectly good Croatian.