My 5 yr old son has red dots on his tongue which he says is so painful he can't eat. he also says his cheeks hurt. what is this?

Most likely: A fungal infection and the moist common is thrush/candida albicans. Please see your pediatrician or dentist for treatment. Very simple to solve.

Primary herpes : We all get cold sore type herpes in our lives. Usually at a very young age and it normally goes unnoticed as a sore. It heals in 10 to 14 days. Sometimes it can be wide spread sores in the mouth accompanied by a fever. In this case it's called primary herpes stomatitis. Watch his fever make sure he can eat and get the lesions looked at by a dentist, pediatrician or pedodontist.