I have a rash on my inner cheek and under the tongue and aburning inside my mouth. what should i do?

Yeast: This sounds like you may have an oral yeast infection. If so, a simple mouth rinse can be prescribed to clear it up. Don't delay in seeing your dentist.

Many causes: Multiple causes including possible virus, vitamin deficiency, an immune disorder e.g. Autoimmune condition. If persistent despite a multivitamin supplement, see a good oral surgeon.

Needs to be seen: These types of situations need to be evaluated with a thorough dental and medical history along with a personal one on one clinical exam.