Don't take him to the petstore to be seen. Take him to an independent, exotic vet and submit the bill to the pet store.
There are 3 basic ways that petstores deal with sick animals.
-take back the animal and offer you a new one. They have already offered you this in a fashion and believe me you do NOT want another animal from them. If you exchange the animal not only are you treating it like defective merchandice they will likely either place the animal in a small cage in the back room with mo medical help to play the wait and see, live or die game or they will send it back to the breeder where it will be treated as badly, if not worse.
-The store staff sees the pig and gives you or sells you some sort of useless vitamin crap. Sometimes they will even give you useless or dangerous antibiotics. These treatments will not help your pet and may kill him.
-they have it seen by their vet which normally knows nothing about
GPs and will often give the wrong medicine or not treat aggresively enough. Usually they make you sign over the
GP to the petstore saying you can buy them back when/if they get well.
DO NOT DO THIS!!!! Many people have done that and regretted it.