The obvious and proper fix is to strip the paint and repaint the entire door, but that costs quite a bit. Do you have comprehensive coverage?

There are some body shops that might be okay with blending it(stripping the paint in just the damaged area and try to match the paint around it) and charge you less for it, but keep in mind that the result will not be optimal and you will probably be able to tell where the blend is.

Another option is, if you are lucky, you can find an undamaged door of the same colour in a junkyard near you. Use car-part.com and try your luck there.

The cheapest way, aside from just ignoring it(derp), is using a paint pen. Probably will look terrible, though.

 

Expanding on what UnknownJinX said if you have Comprehensive and they cover this I would definitely do that. It's likely cheaper than paint, and a lot less legwork than a junkyard pull.

One note on a junkyard door. I picked one up for my project '04 Titanium Grey for I believe $75 from a local yard. However, I had to swap the mirrors and door card between my old door and the junkyard door as my car was a Grand Touring and the pull was from a Sport without the heated Mirrors and leather door card. Essentially there could be more work involved than just picking up another door. The biggest issue with junkyard is having the patience for finding a good part. I am still looking for a good front bumper cover after six months for example.

I would put both of the above options as much cheaper than paint work if you have the coverage or patience/diy skills. I wouldn't bother with a paint pen personally.