Osa mi ništa nije napravila, ali me njezin ubod prošlog ljeta bolio dva dana.

Here napraviti does not mean to make in the literal sense.

In this sentence, Osa mi ništa nije napravila means something like:

• The wasp didn’t do anything to me
• The wasp didn’t harm me
• The wasp didn’t actually do anything to me

So napraviti nekome nešto can mean to do something to someone, often with the sense of causing trouble or harm.

Mi is the unstressed dative form of ja:

• ja = I
• meni = to me (stressed/full form)
• mi = to me (unstressed clitic)

So Osa mi ništa nije napravila literally means The wasp did nothing to me.

Croatian often uses the dative for the person affected by an action like napraviti nekome nešto.

Because the verb boljeti uses a different structure.

In me njezin ubod bolio, the thing that hurts is the grammatical subject, and the person who feels the pain is in the accusative:

• ubod = the sting/sting wound
• me = me (accusative)

So:

• Ubod me bolio = The sting hurt me

Compare:

• napraviti mi nešto = do something to me → dative
• boljeti me = hurt me → accusative

That is why the first clause has mi, but the second has me.

Because Croatian past-tense participles agree with the subject in gender and number.

First clause

• osa = wasp, feminine singular
• therefore: napravila

Second clause

• ubod = sting, masculine singular
• therefore: bolio

So the verb forms match the nouns they refer to:

• osa ... napravila
• ubod ... bolio

Njezin is a possessive adjective meaning her. In this sentence it refers back to osa, which is a feminine noun, so in English we naturally translate it as its:

• njezin ubod = her sting / its sting

Croatian does not have a separate everyday possessive adjective exactly like English its. Instead, it often uses the form that matches the gender of the noun being referred back to.

Since osa is feminine, njezin is used.

Also note:

• njezin is the more standard form
• njen is also very common in speech

Because possessive adjectives in Croatian agree with the possessed noun, not with the English idea of owner.

Here the possessed noun is ubod:

• ubod is masculine singular nominative

So the possessive adjective must also be masculine singular nominative:

• njezin ubod

If the noun changed, the form would change too:

• njezina osa = her/its wasp
• njezino gnijezdo = her/its nest

Prošlog ljeta is genitive.

Croatian often uses the genitive without a preposition for certain time expressions, especially with seasons and parts of the year.

So:

• prošlog ljeta = last summer
• literally something like of last summer, but in natural English: last summer

Similar patterns include:

• prošle godine = last year
• ovog jutra = this morning

So this is a normal time expression, not something unusual.

Because after dva, tri, and četiri, Croatian uses a special counting form for nouns.

So:

• dva dana = two days
• tri dana = three days
• četiri dana = four days

With dan, the form used here is dana.

In the sentence, dva dana expresses duration:

• bolio dva dana = hurt for two days

Yes, from an English point of view it looks like a double negative, but in Croatian this is normal and required.

Croatian uses negative concord, which means that if you use a negative word like ništa (nothing), the verb is also negative:

• Ništa nije rekao. = He said nothing.
• Nikoga nisam vidio. = I saw nobody.

So ništa nije napravila is exactly what you should expect in Croatian.

Croatian word order is flexible, but not completely free.

This sentence has a natural, standard order:

• Osa mi ništa nije napravila
• ali me njezin ubod prošlog ljeta bolio dva dana

A few important things are happening:

1. The little pronouns mi and me are clitics

They like to appear near the beginning of the clause.

2. The sentence puts emphasis in a natural way

• first clause: the wasp didn’t do anything to me
• second clause: but its sting hurt me for two days

Some variations are possible, for example:

• Osa mi nije ništa napravila
• Ništa mi nije napravila osa (more marked/emphatic)

But the original version sounds very natural.

Yes. A learner might also see:

• ubod ose = the sting of the wasp / the wasp’s sting

So these are both possible:

• njezin ubod
• ubod ose

The version with njezin links the two clauses more smoothly, because the second clause refers back to the wasp already mentioned.

The structure is:

• subject: njezin ubod = its sting
• object/experiencer: me = me
• verb: bolio = hurt

So literally:

• Its sting hurt me

This is useful because English learners sometimes expect a structure like I was hurt by its sting, but Croatian commonly says it the other way around with boljeti:

• Glava me boli. = My head hurts / My head is hurting me.
• Zub me boli. = My tooth hurts.

So this sentence follows a very common Croatian pattern.