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
or under the tongue and caused mainly by biting the lips or trauma.
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 also has to be differentiated from a hemangioma then.
Hope it helps.Take care and pls do keep me posted on how you are doing or if you had any other queries.