Hi Baron.
Sorry to hear of your frustration, and hopefully, this will not turn out to be cancer.
I don't know that much about how Medicare works, but I certainly know how much dental procedures can cost, I am retired and couldn't afford to keep my dental plan.
So I have two possible avenues that you may be able to take, within your Medicare insurance.
You might call Medicare to find a General Surgeon, and call them to see if they can do the tongue biopsy.
My other thought, even though you don't have confirmed cancer, is that you can possibly go to a ENT Oncologist? Once again, not knowing Medicare, I don't know what referrals you would need to go straight to an ENT Oncologist. But I certainly think that they could perform a tongue biopsy.
Possibly someone that knows Medicare, can comment on my suggestions, to try to avoid getting this done through dentists or oral surgeons, which I assume you have to pay out of pocket.