have you undergone cleaning of teeth by your dentist?if not get it done.the bump on gum may be due to aphthous ulcer.take vitamin-B supplements.oral prednisolone
tab.can be taken to cure the ulcer.
i advice you to avoid any kind of sour/salty/spicy foods.
as your dentist has checked your teeth,there is no other serious problem associated.
i dont think its dental fistula
.if there is pus accumulation,root planning and curettage can be done for this tooth.
hope you get well soon.