That is indeed frustrating.
Reassuring there is no cancer cell found.
And this is not likely fungal infection either since nystatin did not work.
So, I think you have an autoimmune disorder.
Immune system is attacking the tongue tissue causing persistent inflammation.
You should be tried on a steroid paste in orabase gel like triamcinolone acetonide.
This is prepared by the compounding pharmacies.
Alternative will be oral steroid like prednisone 40 mg daily 2-3 weeks then taper off.
It was my pleasure to help you today.
If I have answered all your questions, Please rate my response Excellent (click on the smiley faces) under this chat box only.
Please bookmark my profile for asking further questions!
This is the link to my profile: