I think you guys need to come up with at least a provisional diagnosis rather than randomly giving him treatment options and confusing him. He should go see a dentist or an oral surgeon (though they will say the same things I have said.)

For me its a mucocele, a mucus retention cyst.

Some more information:

http://health.nytimes.com/health/guides/disease/mucous-cyst/overview.html

http://emedicine.medscape.com/article/1058145-overview