IMO, wait for your appt. I am assuming this lump is inside your mouth. I have one, too - it was caused by biting down hard on my inner lip. Ihave had it for years now with no change. I (don't recommend this) even took thread once and tied it TIGHT around the thing, thinking that no bloodflow would kill it - it WORKED. The thing fell off the next day, no bleeding, no pain. BUT it came back a couple of months later. Now I just leave the thing alone. My point is that this lump could be caused my trauma to the soft tissue in your mouth. Ask your dentist. I was told that to permanently remove it would require oral surgery, which I opted out of.
I think you should get it checked out if it is cancer better to catch it sooner than later. Or if it's an infection you wouldn't want it to spread to your brain