being black, you can always use a black marker to cover it up. but if you get really close, you'll see the different black tone.

second option is to buy a touch up paint. and apply it very carefully. otherwise its blotted here and there and it will look messy.

third option is to cut and polish. will get rid of it straight away (judging from what you said its not deep at all)

fourth option (if you're a baller) just respray the whole door LOL