bump in mouth diagnosis ?

Ever since I can remember, I've had this bump in my mouth. It's inside my cheek (not visible) and just above the lower jaw on the right side of my face. I can even kinda move it around a little with my tonge or my hand. It's never painful, and it doesn't bother me, but it seems like when I come down with a cold or something, it gets larger... not drastically, but it does get a little bigger.
I really doubt it's cancer as I've had it for litterally years and years. I'm 22 and I've had it ever since I was little, but I don't really know what it could be. Maybe a non-cancerous mass? but what could cause it? I also wondered if maybe it's something to do with the lymphatic system as it does seem to grow when I am sick.

Any suggestions or help would be appreciated. I'm really not too worried, but I would like to know if anyone else might know what it is, or if anyone else has experienced anything similar. I've talked to several people and no one has any idea of what it might be...

Thanks in advance!