Pies schował się pod stołem i nie chce wyjść.

Pies is in the nominative singular because it is the subject of the sentence — the one doing the action.

• pies = dog
• nominative is the basic dictionary form

If it were an object, the form would usually change, for example Widzę psa = I see the dog.

Schował się means hid or more literally hid himself.

The verb without się usually means to hide something / put something away:

• schować klucze = hide/put away the keys

With się, it becomes reflexive and means that the subject hides himself/itself:

• pies schował się = the dog hid

So się is necessary here.

This is a question of aspect, which is very important in Polish.

• schował się = perfective: he hid, a completed action
• chował się = imperfective: he was hiding, used to hide, or the action is viewed as ongoing/repeated

In this sentence, the dog has already completed the action of hiding, so schował się is the natural choice.

Because the sentence talks about two different time relationships:

• schował się = the hiding happened earlier
• nie chce wyjść = right now, the dog does not want to come out

So the meaning is roughly:

• first, the dog hid under the table
• now, it does not want to come out

This mix of past and present is completely normal in Polish.

Się is a short unstressed word, and in Polish it usually does not stand at the very beginning of a clause. It often comes after the verb or near the beginning of the sentence.

So:

• Pies schował się pod stołem = neutral and natural
• Pies się schował pod stołem = also possible

Both are correct, but the word order can slightly change emphasis.

Because pod can take different cases depending on the meaning:

• pod + instrumental = location: under
• pod + accusative = movement toward a position under something

Here, pod stołem focuses on where the dog is hidden: under the table.

• pod stołem = under the table

If you wanted to stress movement into that place, pod stół could be used in other contexts. But in this sentence, especially with i nie chce wyjść, the location/result is what matters most.

Stołem is the instrumental singular of stół.

• nominative: stół = table
• instrumental: stołem = under/with/by the table, depending on the preposition and context

Here it appears because of pod used in a location sense:

• pod stołem = under the table

Again, this is about aspect.

• wyjść = perfective = to go/come out once, as a completed action
• wychodzić = imperfective = to be going out, to go out repeatedly, or in a more general/process sense

Nie chce wyjść means the dog does not want to perform that single action of coming out.

That is the most natural choice here.

It can mean either go out or come out, depending on context.

Polish wyjść basically means to exit / to leave a place. English chooses go or come based on point of view.

In this sentence, English usually says:

• The dog ... doesn’t want to come out

because the speaker is focused on the dog coming out from under the table.

In Polish, nie is written separately with verbs:

• nie chce = does not want
• nie wiem = I do not know
• nie idzie = he/she is not going

So nie chce is the standard spelling.

Polish does not have articles like a or the.

So pies can mean:

• a dog
• the dog

The exact meaning depends on context. In this sentence, the context makes it natural in English to say the dog.

Grammatically, pies is a masculine noun, and the verb form schował agrees with that masculine grammar.

In real usage, pies can often mean dog in a general sense, not only a male dog. But if you specifically want to say a female dog, Polish often uses:

• suka = female dog
• suczka = little female dog / female dog in a more everyday tone

Then the verb would change too:

• Suczka schowała się pod stołem = The female dog hid under the table