У мене болить стопа.

Because Ukrainian often expresses this kind of idea with a structure that is literally closer to at me hurts foot than to my foot hurts.

So:

• У мене болить стопа = the natural way to say that your foot hurts
• у мене means something like at me / with me
• the body part itself, стопа, is the thing that hurts

This pattern is very common with pain:

• У мене болить голова = My head hurts
• У мене болить зуб = My tooth hurts
• У мене болять очі = My eyes hurt

English uses a possessive adjective; Ukrainian very often uses this у мене pattern instead.

Мене is in the genitive case.

That is because the preposition у / в requires the genitive in this expression:

• я = I
• мене = me / of me in certain case forms

So у мене is a fixed, very common phrase meaning at my place / with me / I have depending on context.

Because стопа is the grammatical subject of болить.

In Ukrainian, with боліти (to hurt / to ache), the thing that hurts is usually in the nominative:

• стопа болить = the foot hurts
• голова болить = the head hurts

So in У мене болить стопа:

• у мене = who is experiencing the pain
• стопа = what hurts

That is why стопа stays in the nominative singular.

Because стопа is singular.

The verb agrees with the thing that hurts:

• У мене болить стопа = My foot hurts
• У мене болять стопи = My feet hurt

More examples:

• болить with one thing
• болять with more than one thing

So the verb form depends on the noun, not on мене.

Стопа means foot specifically, as the anatomical foot.

Нога is broader and often means leg, though in everyday speech it can sometimes refer loosely to the whole lower limb, including the foot.

So:

• стопа = foot specifically
• нога = leg, or sometimes leg/foot in a less precise everyday way

That means У мене болить стопа sounds more specific and precise than У мене болить нога.

You may also see ступня, another word for foot, especially in more anatomical or precise usage.

Yes, Моя стопа болить is grammatically possible, but it is usually less neutral.

In sentences about body parts, Ukrainian often does not use the possessive word unless there is emphasis or contrast. Since it is obvious whose foot we are talking about, у мене is enough.

Compare:

• У мене болить стопа = neutral, natural
• Моя стопа болить = possible, but more emphatic or contrastive

For example, моя might sound more natural if you are contrasting your foot with someone else’s.

So for a learner, У мене болить стопа is the safest normal choice.

Yes. Ukrainian word order is fairly flexible.

The sentence У мене болить стопа is a neutral, natural order. But other orders are possible for emphasis:

• Стопа у мене болить = emphasizes стопа
• Болить у мене стопа = more marked, less neutral

Even when the words move, the basic meaning stays the same because the case endings and verb form show the relationships.

Still, if you are learning, У мене болить стопа is the best standard order to use.

Yes. У мене and в мене both work.

Ukrainian often alternates у and в for smoother pronunciation. The meaning does not change.

So both are correct:

• У мене болить стопа
• В мене болить стопа

Learners will often hear both in real speech.

A helpful rough guide is:

• у мене → u me-NE
• болить → bo-LYT’
• стопа → sto-PA

So the main stresses are:

• мене
• болить
• стопа

A rough full pronunciation guide could be:

u me-NE bo-LYT’ sto-PA

Also, the final ть in болить is soft.

Mostly, yes: боліти is very commonly used for physical pain, aches, and sore body parts.

Examples:

• У мене болить голова = My head hurts
• У мене болить спина = My back hurts
• У мене болять зуби = My teeth hurt

So this sentence uses a very standard and productive pattern. Once you know it, you can swap in many body-part words.