I know this might not work in your case since you actually cracked the paint, but for future scratches: Go to your local auto store and buy some of the proper wet sanding paper, it's almost like a thin sponge, and soak it in some hot soapy water. Sand down the scratch until you can't feel it anymore (DO NOT go through the clear coat) then take some good scratch remover was and polish it up. This will take out anything that isn't right through the clearcoat.