There are two possible things you can do:
1. Sand the area, then lightly spray your color over it. With newer cars with clear coat, you'd have to also spray a layer of clear coat over the touch up job to make it match.
2. If the nick is small enough, you can take a fine tip brush and brush your touch up paint over the nick.
you won't believe this.......but my wife bought a scratch & sm dent cover up kit "As seen on TV" LOL It comes with primary colors and you mix accordingly. just use a plastic putty knife & spread the cream into sm dents (quater size or smaller) or scratches and allow it to dry. dont worry about excess, the "Magic" solution afterwards buffs it up nicely & some how blends your color matching in with the existing color. UNBELIEVABLE!!! BUT TRUE.....you can find it on AsonTV.com you'll love it, no skills required.
To repair a scratch in the paint of a car is not a easily answered question. It depends on the severity of the scratch. If the scratch is small you can use some of the commerical scratch repair kits or the temp fill in wax. For more severe scratches try sanding the area with 400 grit sand paper and the area around it (about 1-2 inches). Finally @ any Wal-Mart they should have color paint repair kits that will match your paint as long as it's a common color. They have detailed directions on their product. It is best to consult them first. If you dont feel secure sanding your car, I would consult your local auto body repair person and get estimates!!!!!!! Automotive repair ppl are shady so watch yourself!!!
a scratch can easily be sanded out lightly with water using 400 sand paper.then you can buff it out and it will not be noticable
A scratch that's not too deep can be removed with automotive paint thinner and a cloth and some gentle rubbing. NOTE: the area you rub will become much shinier than the rest of the paint. WARNING: automotive paint thinner is toluol, highly toxic to breathe. Use good ventilation.
A slight scratch can be repaired by hand rubbing with a soft cloth and rubbing compound, followed by a fine scratch remover used to take out the rubbing compound abrasions. Rubbing compound is very gritty, and will actually dull the surface when rubbed by hand, but these fine abrasions can easily be removed with a finishing polish.
More severe scratches may need some wet sanding. DO NOT USE 400 grit sand paper!!!! No amatuer at this should sand on their car with anything more coarse than 1200 grit (preferably 2000 grit ultra fine). If you use 2000 grit, you may be able to skip the rubbing compound, and go straight to the finishing polish.
400 grit sandpaper is only for use prior to painting. I have many years of experience in this area, and I stand by what I say.
Be careful using any thinner or solvent on your car's finish. If it is original, it may be ok, provided it isn't lacquer. Lacquer readily reverses to liquid when it comes in contact with solvent. If you have a late model basecoat/clearcoat car, thinner probably won't help repair a scratch, because the finish will not reflow (like lacquer), and therefore it won't have any effect.