A nice narc is a self-obsessed person but in a good sense. This person doesn't harm you in any way or form but would be aware of the things they do and would constantly praise themselves for the amazing things they have done. They would usually do this in front of people whom they are close to with the sole intention of irritating them.
Friend 1: "Bro, that place you suggested for the date turned out to be amazing. You are awesome"
Friend 2: "Thanks. I know I'm awesome"
Friend 1: "Dude stop obsessing about yourself"
Freind 2: "I Can't, I'm a nice narc"