@streetlite What virus did the doctor say it was? What has the oncologist said? Did either of them mention a yeast infection? It’s a very common infection when you’ve had chemo.
Today, you can start using a salt and soda mouth rinse several times a day. Mix 1/4 tsp salt with 1/4 tsp baking soda in warm water. Swish and rinse your mouth really well. Make it fresh every time. I used this and it made everything better. But DO ask your doctors about the white coating in your mouth just in case you need medicine
Will you let me know what the doctors say?

My husband had very painful whitish mouth ulcers after immunotherapy and surgery. They seemed to come on very quickly right after the surgery. He was being treated for thrush but there was no resolution. Finally put him on prednisone and some oral steroid "rinse and spit" solutions. They did a biopsy and found he had Lichen planus. This is not a common occurence. Did they culture or biopsy you sores? The dermatologist is the one who diagnosed this. We also made our dentist aware and she was helpful as well. I hope you get resolution as I know how difficult and painful my husband's ulcers were/are.