Nick/Nicky/Nicki/Nickie/Nickee/Nick-a-roni...aww heck...it's your name, you tell us
If you are happy with Nicole but want something a little more gender-neutral, Nicky will work quite nicely (now you just have to decide how to spell it)
That's the fun of all this...YOU get to choose your name. You might want to try it out for a while and see if you really like it before making it permanent...sometimes you find out that you have chosen your mother-in-law's middle name and you probably really don't want to do that...

(OK, I just made that up, but it COULD happen...LOL)
......Laurie