http://en.wikipedia.org/wiki/Torus_mandibularis
You should never diagnose without an evaluation, but it's likely a torus mandibularis--a hard bony growth on the inner side of your lower jaw between your canines and pre-molars. It's often associated with teeth grinding, though no one is really sure. If it bleeds easily, develops patches of white or red and white tissue, or causes any pain you should get it checked right away, but it's most likely benign.
i have the same thing... a small bump right under my teeth on my lower mandible, someitmes i get soars too...
i was wondering if you received any responses to your post. i seem to have the same symptoms and my dr's are also not worried about it but i feel like it is not normal.