I have a small bump inside my right lower jaw. What could it be?

Must be examined. A bump where you have indicated could be a multitude of things. In adults it is very common to have benign outgrowths of bone called exostoses and are harmless. A bump could be a sign of an infection of either the bone or a tooth. A visual examination, perhaps followed by x-ray imaging will allow the dentist to make a detailed differential diagnosis. Good luck!
Lots of options. There are multiple options for what this could be and more than likely your dentist can do the differential diagnosis and give you the result. It can be a benigh growth of bone all the way to a malignancy. See your dentist asap.