If it's not directly where her tongue flicks, you can try giving her a small soak and letting her swim a little to gently flush the spot (keep her supervised!) And once that's done, a small dab of silver sulfadiazine cream or antibiotic ointment (plain, no painkillers). Keep her on paper towels if you do cause her nose will attract every bit of bedding it can with that stuff. You can soak her a little each day and reapply until it looks less angry. Then cut it back to a few days between soaks.
Hopefully it'll clear up fine in a couple of sheds.
If for some reason it starts to worse, vet asap. Anything like more swelling or weird discharge.