I’ve only seen this once and it turned out to be a prolapse in the organ. It may correct itself and it may not. I would put him in a quarantine tank so no one picks on him and see if it resolves itself. You may try putting him in an Epsom salt bath to see if it pulls some fluid off and reduces swelling. You can put one teaspoon of Epsom salt in a gallon of dechlorinated water which is the same temp as his tank. Leave him in the bath for about 5 minutes. Then place him back in tank. You can do this 3 times a day. That’s the only thing I can suggest. Perhaps someone else will come on with other ideas. Good luck!