See a dentist. Any abnormal findings in your mouth should be evaluated by your dentist. The small bump could be a cyst or extended salivay gland; however, it also could be some kind of tumor. You should see a denist or oral surgeon as soon as possible.
Sublingual gland . You may have a stone in your sublingual salivary gland. This usually causes pain and swelling. It is a good idea to have a dentist or doctor look at any unexplained bumps in the mouth, whether is hurts on not, to rule out oral cancer. If it is a stone, your dentist/doctor may try to 'milk' the stone out (this is painless) or have you suck on lemons or hard candy to activate your saliva glands.