I'd start with a flat screwdriver to get down to the meat. If that is too scary, use a stainless steel wire brush from Ace. Then before you touch it up, sand it til its shiny--probably plenty of metal there. My people tell me that production bikes are overbuilt and therefore I don't worry and only try to make it look "nice enough" But if it is really deep, it bugs me.

AND ummm, is there a picture of the whole bike? Drive side please.