You most often judge a wound by the size. How big is it? Are there loose pieces of skin/tissue? Has the bite gone through the lip/cheek?
You clean wounds, that’s important. You can rinse it with human eye wash (saline). Small superficial wounds can as a rule be treated at home with plain neosporin cream (the type that doesn’t have a painkiller) and daily rinsing with saline. A close eye must be kept. Any swelling, excessive redness or seepage requires vet care, because it means a bacterial infection could have taken hold and the bun might need oral antibiotics. Obviously signs of pain also needs vet attention and a painkiller. Signs of pain are often loss of appetite, marked inactivity, teeth-chopping, tendency to hide and to avoid interaction.
Rabbit wounds can form abscesses. The risk is biggest with puncture-wounds, i e wounds that heal over quickly so bacteria trapped inside can thrive in an oxygen-free environment. An abscess is a pocket that fills with pus. It can grow quickly and always requires vet care, because rabbit pus is thick like toothpaste and won’t drain easily.
It’s of course always safest to have a vet look at wounds.
If your buns are together you might have to spearate them but keep them side by side. This is so as to avoid over-grooming of the wound by the other bun.