Sorry, I can't comment on the vasectomy-specific side of things, but my experience with surgery involving a larger body area is that the nerves can and do grow back. I'm pretty sure that healing effect would be more noticeable for a vasectomy where the incisions are comparatively small and the area enjoys a good blood supply. But by all means, get him to talk to the urologist for reassurance, especially if he's still having some pain at times. But it may just be a case of needing longer to recover. Surgery is *always* an assault on the body.

PS - as a believer in energetic-medicine, I'm inclined to comment that surgery can disrupt the energetic anatomy too. Remedial energetic strategies could involve reiki or similar, yoga/chi kung/tantric breathing exercises, and even acupuncture/acupressure. HTH