I would book an appointment with a Dentist and explain what is happening. They will be able to tell if it's causing any damage already. You could also book him into a GP and explain what has been happening. They would look at his tonsils, if you still have concerns, push for a referral for an ENT. At least then you have one and can use it if things don't improve. As I mentioned, the Dentist may even pick up something, my neighbor found out about her sons tonsils through her dentist and it was only then she realised he had been teeth grinding.