My husband was 35 yrs. old non-smoker and non-drinker and was diagnosed with tongue cancer in October. His started out like your son's. His was a white patch under the right side of his tongue near the base. He had surgery on Nov. 21st to remove 1/2 of his tongue and 42 lymph nodes on the right side of his neck. (That was a precaution, no cancer was found in the lymph nodes). In December he started Radiation Treatment and completed it last month. Unfortunately he has another white patch, he found it on Saturday and he goes to the ENT on Friday.
The best advise I can give you & your son is to go to the ENT as soon as possible to have it checked out. A biopsy is relatively painless and then you'll know for sure. I can understand you being worried, I'm in the same boat but you have to stay optimistic for him. If you ever need someone to talk to, I'm here for you.
I'll keep you in my thoughts & prayers.
Good luck,
JudyB