Josuke's Stand grants him the ability to fix and restore pretty much anything -- including people! This means he's capable of healing someone fully no matter the damage, and get them back in top condition in pretty much a second. The only limit to this is literally death -- which means he can restore limbs, fix broken bones, and so on! Crazy Diamond can't however cure illness, just injury.

Typically, he's honestly the kind of guy who would heal passerbys if he sees them injured, so if you want a quick and easy heal and would like Josuke to take care of it, feel free to lave a comment here and we can either handwave it or play it out!