Why is my dog's nose peeling and hard?

His nose is black, and it started to peel and some of it is now pink. He's healthy, and goes to the vet regularly. He's 5 years old. He's a shih tzu labradoodle. It's also hard, but when yuo touch the pink spot, it doesn't seem to hurt him... He got all the shots he needs. His brother's nose isn't doing this. Is there anything I should do?? (We haven't gone to the vet yet so they don't know about his nose.) Thanks!! :)