it depends on the severity of the wound. If it's a simple surface bite, that's not deep and with no tearing, it might heal fine. But if the ear is torn and/or the wound is deep, it would need to be evaluated and possibly stitched by a vet. Then there's also the possibility of a bacterial infection developing, which would need to be treated with the appropriate antibiotic.
I'm just giving you a guess of what i might do in a similar situation, but i haven't seen the wound and i'm not a vet, so when in doubt it's always best to take your bun to an experienced rabbit vet to be properly checked.
http://rabbit.org/vet-listings/