One possibility for your symptoms is mucocele. It is a rubbery, bubble like 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. It then has to be differentiated from other mucocutaneous lesions also.
I hope it helps . Take care and regards.