Ako osip bude veći, morat ću opet doći doktorici.

In Croatian, after ako when you are talking about a future condition, you normally do not use će.

So standard Croatian says:

• Ako osip bude veći...

not:

• Ako osip će biti veći...

The form bude is the special future-oriented form used in clauses like if, when, as soon as, etc. In English we do something similar in a different way: we say If the rash gets bigger / If the rash is bigger, not If the rash will be bigger.

So this is a very important pattern to learn:

• Ako + bude / dođe / vidi / napravi...

when the condition refers to the future.

Osip is a masculine singular noun.

Because it is the subject of the clause, it is in the nominative:

• osip = rash

The adjective has to agree with it, so you get:

• veći = bigger, larger

not:

• veća (feminine)
• veće (neuter)

So:

• osip bude veći = the rash is/gets bigger

Also, veći is the comparative of velik (big), and it is a bit irregular. Croatian does not say velikiji.

It can feel like either, depending on context.

In a sentence like this, Ako osip bude veći... often naturally corresponds to:

• If the rash is bigger
• If the rash gets bigger
• If the rash becomes worse/bigger

Because this is a future condition, English often uses a more natural translation like gets bigger, even though Croatian literally uses bude with the adjective.

So the Croatian structure is broad enough to cover the idea of a future state that may happen.

Both are possible in Croatian, but they are structured differently.

You can say:

• Morat ću
• Ja ću morati

When the future auxiliary ću comes after the infinitive, the final -i of the infinitive is usually dropped:

• morati + ću → morat ću
• doći ću is not used this way because doći behaves differently and future is usually formed another way in practice

In your sentence, the main clause begins with morat, so the clitic ću comes right after it:

• morat ću opet doći doktorici

This is a very normal and natural Croatian pattern.

Because ću is a clitic. Croatian clitics usually go in the second position of their clause.

Here the sentence has two parts:

• Ako osip bude veći,
• morat ću opet doći doktorici.

After the comma, a new clause starts. In that clause, morat is first, so ću goes right after it:

• morat ću

That is why you do not get something like:

• Ako osip bude veći, ću morati... ✗

Clitics cannot normally stand at the very beginning of a clause.

Doktorici is dative singular of doktorica.

• doktorica = female doctor
• doktorici = to the female doctor

After verbs like doći, Croatian can use the dative for the person you are going to see:

• doći doktoru
• doći doktorici

So:

• doći doktorici = to come/go to the doctor

A learner might expect doktoricu, but that would be the accusative, and it is not what this verb wants here in this meaning.

Yes. Doktorica is a female doctor, so doktorici means to the female doctor.

If it were a male doctor, you would say:

• doktoru

So the sentence specifically refers to a woman doctor.

In everyday Croatian, people may choose between words like doktor/doktorica and liječnik/liječnica, depending on style and context.

Yes, doći basically means come / arrive, but in Croatian it is very natural to use it when talking about reaching a person or place, even where English would often say go.

So:

• doći doktorici

can naturally correspond to English:

• go to the doctor
• come to the doctor
• go back to the doctor

depending on context.

Croatian often focuses on the idea of arriving at the destination, while English more often chooses between come and go based on the speaker’s point of view.

Opet means again.

In this sentence:

• morat ću opet doći doktorici

it means the speaker will have to go/come to the doctor again.

Its position is fairly flexible. For example:

• Morat ću opet doći doktorici.
• Opet ću morati doći doktorici.

Both are natural, but the emphasis shifts slightly:

• morat ću opet... can emphasize the repeated visit
• opet ću morati... can emphasize the repeated necessity/obligation

So Croatian word order is flexible, but the chosen order affects what sounds most prominent.

Yes, very often you can.

For example:

• Morat ću opet doći doktorici.
• Morat ću opet doći kod doktorice.

Both are natural.

The difference is roughly this:

• doktorici uses the dative and is a compact verb + person construction
• kod doktorice means more literally to/at the doctor’s place and uses kod + genitive

Learners should know both patterns, because both are common in real Croatian.