I believe there are nose butter products for dogs as well. Is the dog light in color or been in the sun often recently? It could be from too much sun. I usually associate dry noses with very short-faced dogs or very old dogs, so it may be worth bringing up to your vet if it persists. It could be some kind of imbalance that would show up on bloodwork.
First time Chihuahua owner with many years of dog experience!