Doesn't seem to be serious to me
If it is since last 2-3 days only and is painful then it might be because of
vitamin b 12 deficiency or because of bite by teeth
In those cases it will heal completely with the medicines I have given
Next Steps
if the ulcer happens repeatedly or
If it is there since long duration
Or he has a history of cigarette smoking or tobacco chewing
then you should consult a ENT surgeon