Thanks for the replies everyone. I guess i'll just hook up a 5v source to the nano.
I was asking because I already soldered a 12v source but I'm afraid I'm afraid I might be over working the regulator so I also wanted to add a fixed volt regulator to the 5 volt source. I had a problem with my nano restarting and the L led light flashing rapidly which turned out to be a bug with the watchdog timer and the Chinese nano's. I burned an UNO bootloader to the nano which seems to have fixed it but my nano will cut off momentarily here and there as it is controlling my fuel pumps. I just tried plugging in a 5v usb power bank and tested that without 12v power input and it seems to be working with no interruptions unless I just got lucky in those 2 min. lol. Hopefully this will fix my issues.
Thanks again guys.