[Lucy Dog]

Here's a couple articles regarding your question. It can be a symptom, but definitely not an absolute indicator of a sick dog.

Dog noses - myths and facts about your dog's nose - weekly pet tips by Pets.ca | Pets.ca

Does a Dry Nose Mean a Dog is Sick?

Does My Dog's Dry Nose Mean They're Sick? | Dog & Cat Health, Wellness, Products and Breed Information