Greg,
Would you mind answering a couple of questions? I may be able to help shed some light on your "lump". I was a little confused for the same reason Jerry was on your post. You have cleared that up so...
You have clarified that it is on the lower and on the interior part of your gum. Right or Left?
How far back? (beside farthest back tooth, halfway by middle teeth, behind front teeth)
How did you become aware of it? Can you see it when you look in a mirror and what does it look like? (size, shape, color etc.)

Just trying to help you figure this out. Be careful of the information you find on the internet there is a lot of poor advice.

E-mail or PM me if you think I can be of assistance.

Cheers,

Mike