I think it might be mild orf too.
My Shetlands currently have it on their noses. Mind you, it's on the bridge of their noses, those that have it, not near their lips which is where I've seen sheep with it before. Then again, it could be rainrot (Dermatophilosis)
I don't think it's anything very serious, though as Fleecewife says, just careful not to touch your own face until you've washed your hands after dealing with the sheep, just in case it is orf.