Probably not the best thing to do, but I banged, or rather used a pair of pliers to fix a rim once. I still use the wheel but consider it significantly weakened. I don't use it for any high speed stuff anymore. It is a freewheel and the only reason i straightened it was because it messed with the brakes. If yours doesn't use a brake I would probably just let it be. Bending it again will only further weaken it. I'm not a mechanic, just letting you know my thoughts on it.
Edit: I'm guessing the bike shop would say the rim is garbage now.