Couple of things -

The sores may get "bigger" but also my increase in number. Try a salt water rinse with warm water several times a day. Also ask your doctor(s) for a medicated mouth rinse with lidicade (sp) That will help

Radiation burns / irritations - try any type of topical creams with vitamin E and aloe. Stay away from soaps that dry out your skin

These are just some rocks in the road. Nothing more. Nothing less. Focus on the destination, (becoming cancer free), and these obstacles will become minor annoyances. Unfortunately, you will encounter more issues before the healing and recovery starts. Bear down and get through it.

Good Luck - (You can do it!)