I would always suggest having them looked at - it can't hurt. However radiation is cumulative - a few weeks a few radiation (depending on the person) is the worst time. Plus you are dealing with very sensitive traumatized tissue. Anything can irritate it - point in fact. My real tongue (half of it is a graft) my real tongue was irritated by an upper molar for the better part of my rads - it got worse as rads progressed - my upper molar is inset - so it was in a position where because of the swelling etc my tongue was being pushed into it constantly. I was very conscious of it so much so that I would sleep a certain way to prevent it from rubbing at night - I finally asked my dentist a few months post radiation to please File it down, he did and the problem for the most part was solved - that area is still sensitive 7 mos out of radiation! But usually only when I eat foods that irritate it. Rough foods, dry foods, spicy foods, or acidic foods! Some people take longer to heal. So If your brother has tried to get back to eating and is still healing ths could very well cause ulcerations and issues! But it is always a good idea to have it checked out. Good luck!