no need to repaint the whole bumper. I had a similar (but larger) scrape on my bumper and I repainted just that corner with pretty decent results.
http://www.g20.net/forum/showthread....&threadid=4409
I never did put a clearcoat or anything over the new paint. I'll tell you up front its not quite as shiny as the original paint, but unless you know where to look you cant tell that it was ever repainted.
edit: The actual paint I used was called import color or something like that. It said nissan aztec red on a sticker on the lid, and matches my old paint very well. I got it from advance auto, along with some primer.
