I have heard that sometimes your saliva gland under your tounge can become clogged with a stone that just randomly forms. It is very painful and causes swelling and a bump. I know that there is an old remedy for it and it is to simply eat lots of sour things and it will force itself out. Just a thought, could be a possibility. I hope everything works out for him, poor thing. :(
I have the exact same thing. I have been like crying in pain because of it. It hurts to move my tongue around and it makes it hard to swallow even my own saliva. I have been to my doctor and dentist about it, both saying it will leave on its own..but it has been years...They said its a salivatory stone, caused by plaque type buildup that gets stuck and makes it hard to salivate...who knows. I wish I had an answer for you, and for myself.