You've done the main thing in separating her. Simple first aid for the wound, while she is separated, is fine. I clean with soap and water or saline and apply a little Neosporin. Don't use a cream or ontment with a "caine" drug in it (added as a painkiller.) BluKote is also good, and masks the red color of the wound so they won't pick on it when you put her back. It's an antiseptic besides coloring skin bluish purple. Usually with a minor wound it is safe to leave the bird wth her flock if you have BluKote for the wound -- but observe for a bit, because sometimes they will peck anyway.
You may want to remove the rooster for a few days when you put the wounded girl back, or before. Hopefully this will calm hm down a bit. He should be well away from the hens when segregated. Or, you may decide he is simply too rough on his hens and needs to go -- some roosters are like this.
