Disclaimer: I am not a doctor - follow at your own discretion.
In your situation, you can use a cool compress, (not ice, just cool) a mentholated lip ointment, (My favorite is Blistex, but plain Carmex with the yellow cap and porcelain jar is good too) and an over-the-counter med like ibuprofen or aspirin. With the ibuprofen you can actually take quite a lot of it without harm to yourself as long as you don't do it for too long - we're talking weeks, not a day or so. The maximum allowable dose for a grown male is 800 mg, four times a day. That's four 200 mg tablets - you'd probably do well enough with 3.
Regarding these comments about how you should be in shape to begin with, whatever - sometimes the demands of the playing situation will tax you even if you are in shape. Back during my time as a military bandsmen where I was routinely in rehearsals up to 6 hours a day, one time we had a day where we literally had 3 gigs - 2 full ceremonies (lots of military marches) complete with pre-music, honors, colors movements, bugle calls, etc, and we capped it off with a full concert band concert. By the time the day was done, my chops were about as spent as they had ever been and my chops were in great shape at the time. And then we had another gig the next day before we got a couple of days off. I had no choice but to make it happen the best I could.
Good luck to you! Keep us posted on how it works out.