I would suggest you to go for an X-ray (IOPAR) for the same area. This will give us the right information, as he is 11 year old & it should have erupted till now but sometimes due to early extraction of milk teeth, the eruption of permanent teeth gets delayed.
Next Steps
Visit a dentist and get an IOPAR/OPG done.
Health Tips
First line of treatment would be to go for an X-ray.