Weird bump in my mouth?

A while ago I found a little bump in my gum. It was like a zit inside my mouth. I know the thought of it makes me gag. Anyways every other day I'll notice its back and I popped it and I do heaar it pop. (gross) So today I was eating chips and salsa and I then noticed that it was bigger. It went from a pin point to a eraser, like on the end of a pencil. Can anyone tell me what it is.