From what I've been told if it goes away within a few days it is nothing to worry about (from a cancer standpoint) but that was in reference to the tongue. My thoughts: Go to the Doctor/Dentist and inquire. Nothing you will receive here will be even close to worth the assurance of a professional.
Might cost a bit of money, but it will cost far less than ignoring something that could be potentially serious based on the advice/opinion of a bunch of forum nitwits.
As with any question posed on the internet, you are only going to get a bunch of different answers that range from "It's nothing to worry about." to "You're totally doomed." and will have you yo-yo-ing back and forth between reassurance and sheer terror. I'd say see someone who's education, training, and liability influence their diagnosis.