How to fix small scratch in my car?

if the scratch has just gone through the clear coat and looks like a small white one then a touch up pen with clear lacquer and a good buff up when its dried will sort it out. if its gone down to primer or even metal you’ll need paint that's colour coded to the car, either in a touch up pen or spray can, and cover the mark then same process as above. if its large enough that you don’t think it will be covered then get the panel re-sprayed.