You have rust on it? That a bad scratch. Normally what you shoudl do is get fine grit sand paper and lighlty polish the rust and 1mm to either side until it's off the body then apply the paint and then the clear coat to even it out.
I've never had a steady enough hand to get evernything leveled out and pretty after such a repair. However, I had one done by a relative with very steady hands and it looked as good as new, so it's possible.
Update: If you think it's from the other car you can try to clean the area first with a soft cloth and some dish soap and water like you would before you wax the car yourself. If it doesn't come off the above will work, as long as it's fine grit (1600 or higher) you work on it slowly so you don't take out too much.
Last edited by nameless00; 01-08-2010 at 10:59 AM.