I just updated my NCC to the latest version, and I made the mistake of leaving the NIS running while doing that.
So now when I try to start up the NIS, it tries to start up and then stops right away.
How do I fix this?
In the meantime I exported for the 'lightwallet' from the NCC and downloaded the Nanowallet. Would I be able to now disregard running the NCC wallet which I'm having problems with, turn it off and only use the Nanowallet? That kinda of seems to be the case to me. I like this nano wallet, already tested sending some coins

You might have corrupted the NIS database when updating while it was running although it is unlikely. You now have several options:
1) You can switch to Nano Wallet
2) You can delete the NIS db and sync from scratch
3) You can change the ncc config to use a remote NIS
Choose whatever you like best.