Sounds to me like it could also be a clogged salivary duct. I had one a few years ago. It was very painful, and it looked basically like I had a pimple under my tongue. The whole area swelled up, I saw an oral surgeon, and he said that if it keeps coming back he will remove it. So far it has not come back. My dentist recommended sucking on really sour candies to make myself salivate more and force out whatever was clogging it. (sometimes a piece of food can get stuck). That worked. One day I noticed a little tiny hole where the "bubble" had been. Apparently whatever it was went away on its own. I sucked on lemon drops for a few days, and wrinsed with salt water to prevent infection. It came back once after that, and I did the same thing and it went away and has not come back since, knock wood.