Any signs of disease, be it physical or behavioral?
Clowns are just that..clowns. He may have decided he likes that particular spot. My percula is pretty staionary. She tends to hang out in her nem and never leaves other than to eat. She's currently back in qt and again, other than to eat, she stays within "her" PVC elbow. I also have two black and white ocellaris clowns that are more active. They spend the day flying all over the place.
If there's no other fish in the tank harassing him and he's not showing symptoms of disease, I'd be inclined to let him just hangout.