I suggest you keep your gums clean and don't irritate it too much. Gargle salt water can help, and call your dentist and tell them and see what they suggest. They may want you to go in and have it checked out. But call them they can give you the most accurate advice.
I have the same problem pal. A little hole behind my last upper tooth. I've never had nor seen anything like that so I began to panic a little. I noticed it just recently, ok, a year ago. It hurts when I brush my teeth, and one day I was riding a bike, chewing bubble gum on the side of the mouth where that hole is. Suddenly, blood started to come out I was riding the bike and spat blood at the same time, all over the road. I was chewing the bubble gum simple coz some bad taste is coming from that hole. I think you know what I'm talking about. Then I read on the internet it's just a wisdom tooth coming out. But as we all have different opinions- some people said it's gum cancer. When I've read gum cancer I was thinking about committing a suicide. That thing is nasty, spread all the way to the heart, damaging it. Others again say, just a gum decease, gingivitis. AND WHAT OF THOSE THREE IT COULD BE? I'm 19 years old now, and I'm in dilemma about visiting my dentist, as it could maybe be my last days of healthy life. I suggest you do that too. And if some dentists are reading this, I beg you: Please write your opinion here, tell us it's nothing dangerous. Please.
I have a hole in my gum and I just had my wisdom teeth removed, but the hole is about a my third tooth up from the back...what could it be?