What should i do if i have an unusual sore under my tongue. what might it be?

More info needed....: How long has the sore been there? A week, a month, or a year? Smoker or dipping tobacco user? Without seeing the lesion and answers to these questions, its hard to tell what it might be. If it has been there longer than two weeks, see an oral surgeon for an evaluation.

Many reasons: Could be from trauma from rough foods for example. Or infectious like bacterial or viral infection like herpes , how long you've had it? If it lasts more than 2 weeks and did not go away have it checked by a dentist