***Edit: Will NOT wipe away***
Most likely it is a case of Leukoplakia, where chewing tobacco is usually the cause.
And if it is Leukoplakia indeed, then there's up to 20%
risk of turning cancerous over time.
It is highly recommended to abstain from tobacco use and alcohol consumption.
There's also the possibilty of oral thrush, however, my money is on the former suspicion.
Best wishes,
Niko
Stay away from tobacco as it will worsen the situation more. If you are not sure what exactly it is, consult a doctor. Better to consult a oncologists at radiation centers