Hyperkeratosis it occurs due to a protein inside your dog called keratin. It sounds scary but it's common it can also affect the nose. If you Google [Hyperkeratosis dog paw nose] you should be able to find a ton of information on it. Snout and Paw Soother will help in preventing it. It may be worth mentioning to the vet though. Underlying medical conditions can cause it but I would venture to say it's genetic.