I really love this name. Very simple, mysterious, and cool. It’s quite common but this name is really good! If my name was Niko, I'd feel like i can rizz up everyone lol!
This name actually sounds feminine to me when spelled with a k instead of a c since i am used to names ending in "ko" being feminine because I'm used to Japanese naming rules. My brain has difficulty thinking of this name as masculine only but i don't really care about fitting in with how i think.