Hello,
Without examination,it is difficult to confirm a diagnosis,but from your description it looks like a mucocele.It is a rubbery, bubblelike painles swelling. It is usually inside the lower
lip,under the tongue or the inside of mouth and caused mainly by biting the lips or trauma during eating of food.
Usually it goes away on its own.But if it does not,then corticosteroid injections and surgical removal by scalpel or laser are done by a dermatologist.