I have a flap of gum on the lower inside part of my lower gum (where the floor of the mouth meets the gum) covering from near my front teeth and wisdom tooth. If I dig my tongue deeply into the floor, I can lift up the flap just a bit. The flap is painless, but it has appeared out of nowhere and must have come to be very quickly. Do you have any idea what this could be? Thank you very much!