OUCH, poor thing! Most of the time when you try putting topicals on areas like that, it draws more attention to the area and they just want to lick it off. While licking wounds in and of itself isn't entirely beneficial, as long as she isn't rubbing it or excessively licking the area, it should heal fine on its own. That's a really difficult area to treat, though, as no matter what, even if she isn't trying to lick her nose, she will lick it inadvertently after eating, etc. Probably doesn't even warrant a vet trip unless it gets infected.

It COULD have been the wire... at least, for your (and her!) sake I hope that's all it was!