I didn't clue in on his age - if he doesn't get treatment now it will continue to get worse and he may lose function in those hands before long.
Many people don't realize that there are over 100 different types of arthritis. Most think that it is all osteoarthritis which is due to age and use of the joints. Other than replacing joints and pain meds there is not a lot that can be done with that. However, if his issue is something like Rheumatoid arthritis, they can stop the deterioriation from getting any worse and use anti-inflammatories to help the pain. With swelling there is a good chance it is something like rheumatoid. And even young people get it. Perhaps this will help him to get to the doctor. At the very least he might want to try some NSAIDS (aspririn or ibuprofen) to see if the anti-inflammatories in those can reduce his swelling and pain.