My new mouse was attacked by his cage mate and has a little gouge taken out just above the tail?

I'm not sure what to do because he is so small. It is no longer bleeding and he doesn't appear to be bothered by it. I have the two boys seperated now. The other mouse is slightly bigger and looks a mite older than the injured mouse. Should I clean it? Should I leave it be? I plan to monitor it multiple times a day. The little guy is sitting with me right now tugging at and grooming little areas of my dress, I love him to bits. Any advice?