A bad jam can throw the timing out of whack. Seems to me this may be why the needle is hitting something metal -- bobbin and needle may no longer be synchronized.
Have you taken a flashlight to the bobbin area (with bobbin case removed)? Sometimes a tiny bit of thread gets caught in the mechanism. If you can't see anything, or see a bit that you can't remove with tweezers, you can try using sewing machine oil on the area to soften up the thread.