There is nothing wrong with wanting to keep any magic ability off your Nord Warrior.
I
have a Nord Warrior as my only character so far, and he doesn't use any magic except the occasional healing spell. I haven't spent a single level on magic power.
But worrying that having one skill number tick up by a total of one is ruining your character ceases to be role-playing, and becomes character-sheet OCD, sort of like those people who have to keep their house antiseptic or they can just
see the little germs crawling around.
Having a magic skill bumped from 15 to 16 by a skill book is utterly meaningless, and doesn't undermine the not-a-mage-at-all nature of your Nord Warrior, especially since, as far as I know, ALL characters start out knowing a few spells and having magic skills that are greater than zero.