When your teeth are infected it's hard to know if the infection is going to go. Ideally they'd have put you on antibiotics before removing the teeth or drilled in them and let the infection drain out.
Nasty but tooth infections are very serious. We lost a little 9 year old boy in a nearby town when a tooth got abscessed and the infection went to his brain. He died in a few hours.
I would say you need a good antibiotic that works on mouth infections. I don't think I've ever heard of anyone taking Nystatin for tooth stuff. My dentist has given me antibiotics that work very well on it and I've never taken Nystatin.
Please ask your pharmacist to help you find a better antibiotic. If you have allergies they might have put you on the Nystatin instead of a better one.