Have you heard of amplified pain? It's essentially another name for what your doctor is telling you - the nerves get so used to sending pain signals, that even once the inflammation is gone, they continue to send them and the child continues to be in pain.
It's very real pain. My daughter has both IBD and a form of inflammatory arthritis, and for years her arthritis was completely out of control. We finally got her arthritis under better control but she continued to be in severe pain.
We did outpatient PT and psych but her pain was still out of control. She was not sleeping, missing a lot of school and was just miserable all the time.
So then we did an intensive pediatric pain rehab program. It essentially teaches kids how to live with pain - how to function despite pain. It is also supposed to "retrain" the nerves and over time, as they get more functional, pain is reduced.
There are programs all over the country. Ours was 3 weeks, inpatient for 2 weeks, day program for 1 week. It is intensive PT/OT/aqua therapy/group psych/CBT and that kind of stuff to get the child back on his/her feet.
It REALLY helped my daughter. She went from not sleeping all to falling asleep normally - within 20 minutes (she had been lying awake for 5-6 hours every night). She became much more functional and learned how and when to push through the pain.
She has now completed 1 year of college. It was tough, but she got through it. She now has lots of tools - ways to cope with pain - instead of missing school and activities she loves.
These programs generally do not use meds - if the kiddo is on strong pain meds (opioids) they try to wean him/her off them. They sometimes add meds for nerve pain - like Elavil or Lyrica or Gabapentin.
But mostly it is a non-med approach.
Many of the big children's hospitals have them.
There's a great book called "Conquering Your Child's Chronic Pain" - we were given that to read before doing the program. I would definitely read it if you can - you can get it on Amazon.
And if he continues to be in a lot of pain and is missing school and is basically not functional, then I would definitely look into a pain program. Some are outpatient, some are inpatient, all are intensive.
But the program really helped and changed my daughter's life for the better.