Book with a female main character and a male protector after a nuclear or chemical fallout

I thought it was a Stephen King book but I can’t find it in his list.

I can’t remember the exact plot but I know the main character and her protector, as well as many humans, developed growths on their bodies, after time the growths eventually break off and reveal they were transformed, specifically one of the bad guys of the book is turned into this lizard/snake thing as he is very manipulative towards people; the transformations are meant to reflect their inner personality.

The girl’s growths reach the point where she can barely see and breathe​, but when they break off she has some kind of aura or something and inspires those around her.

I’m not sure about the cover, the year would have been late 90s, early 2000s, and it was a known book at that time.