Problem is most rims are cast, so they brake easier when hit then forged. You could try using a rubber or plastic mallet but after a hit like that it might break the piece off. Not to stay that it's impossible. If it were me, and I'm not well versed on rims, I would try using a plastic mallet on it while the tire on and with pressure. Or hold a piece of 2x4 on it and hit it with a mini sledge. But that's just me, some one else on here my have a better option.
---------- Post added at 03:20 PM ---------- Previous post was at 03:14 PM ----------
Actually I looked at it better and i idk if you can really do to much about that. You could try a hammer and a punch to knock it straight and sand down the marks.