Is there any size or shape change in bump?Do u remember any injury associated with it?

Your description points towards the diagnosis of mucocele or a ranula. But these are tentative suggestions only based on your description without a look at the clinical picture of the affected area. These lesions never cure on their own, although they might get traumatized periodically and can burst open and it will seem as if they have subsided. But because these are balloon like structures under the mucosa of the oral cavity they will get refilled and retain the previous size again, and can be sometimes bigger than the previous size. The only treatment is removal of these entities by an oral surgeon for permanent relief. Absence of disease does not always indicate absence of Pathology, so you should not wait for the symptoms to appear before seeking treatment. Regards.