I recently developed a sore on the underside of my tongue. It is a very small, circular white patch in the middle. It sometimes oozes a teensy amount of white mucus-like substance. I have a tongue ring in my mouth and the spot is right next to the bottom tongue ring hole. I don't know if it could be a canker sore because it is not lined with a rim. I do not smoke and I am 23 years old. What could this be?