What Causes Brown Bump On Chin?

I had a brown bump on my chin that looked like a mole that I think arose in a place where I had popped a pimple. Periodically the top of the mole-looking bump gets loose and falls off, and it usually bleeds a lot and I usually try to clean it with peroxide. It just came off again and it had been bleeding a great deal, but now the spot is almost black...do you know what the problem is and what I should do about it?