I can help with this question! My eardrums have ruptured more times than I know. My mother says it is a miracle that I am not deaf. Recently my nephews eardrum ruptured, which I was sad to hear. I have a five year old daughter myself. Whenever I take her to the pediatrician I always ask about her ears. They always look fine but last week her eardrum ruptured! I understand what you are going through.
Anyways-I know it was back in the 80's, but my mom struggled with the same problem you have. She wanted me to be a normal kid and be able to go swimming. Doctor after doctor told her that I could not go swimming-ever. She even washed my hair in the kitchen, while I laid on the counter with my head over the sink! Finally she convinced a doctor to get earplugs for me. The thing is you need to make sure that you go to an ENT (ear-nose-throat) doctor to have earplugs made especially for your son. Do not just buy ones at the store. A doctor can have a mold made of the inside of your son's ears. Then plugs are made with a dot on one to identify the left from the right! I don't think I ever had any problems after the earplugs. However you might not let him dive off the diving board. The doctor told my mother that could rupture my eardrum!
I would consult your physician as to when your child's ear is healed. If ear problems persist he/she will probably have you contact an ENT doctor.