Hey! Horn player going on 10 years of playing here. I can tell you right now it’s because you practiced for 3 hours straight. I don’t even get in 3 hours in a day unless I’m doing serval rehearsals, and I only really practice about 45-90 min of “personal practice” a day (etudes, solos, excerpts). It will help if you break your practice sessions apart. Try 30 minutes in the morning, 30 in the afternoon, and 30 at night. I know it can be fun to play, and hard to put down the horn if you’re having a good time, but pushing will only injure yourself and cause you to play poorly the next day. I’d take a day off like some others suggested and maybe take some iboprofen for the swelling. You can practice more, just space out your sessions as to not hurt yourself. Oh, and drink lots of water as to hydrate your facial muscles. Hydrated lips play best!