Ibhave a few ulcers under my tongue what's the best treatment they are very sore?

Aphthous Ulcer: Go to pharmacy and pick up very small tube of orabase or kenalog (triamcinolone) in orabase. Apply as directed.

Depends on what itis: It really depends on what it is. Usually the ordinary sores, such as aphthous ulcer or canker sores resolve on their own within 7-10 days. If the ulcers last longer, they definitely need evaluation, especially if they are under the tongue. Some ulcers may even need biopsy. See an oral surgeon for the evaluation.