His butt has been hurting him. could it be this sciatic nerve pain?

Possibly: True sciatic nerve pain typically manifests from compression or irritation of the sciatic nerve by the piriformis muscle, which is in the upper buttocks. However, true sciatica typically results in pain in the distribution of the sciatic nerve, which is down the leg. Thus buttocks pain can be due to piriformis spasms, even in the absence of sciatica down the leg.

Many Possibilities: Depending on how long it's been going on, i would consider an evaluation by a spine specialist. Sometimes it could be a muscle imbalance, early onset arthritis or scoliosis. Also could be a pinched nerve/herniated disc. Either way it might be good to figure it out and get appropriate treatment.