Something on my gums?

There is some kind of sore that's on the front gums right by my back molars, in between my cheeks. It's been hurting a lot the past few days; it hurts to eat, sometimes to talk as well. Just wondering what it could be? its whitish around the rim, it looks like a hole but its really small. the inside is like a blackish grey color. What should I do to get rid of it?