You have to mention signs of illnesses that your dog is showing. Cold or warm dry nose in dogs are not signs of illnesses. Both warm and cold noses are normal. Your dog can be normal without any diseases with dry and warm nose and can be sick with cold nose. So, evaluating the nose temperature is not a diagnostic tool for any illness in dogs. If your dog is showing symptoms like loss of appetite, shaking, panting, lethargic etc regardless of nose condition then visit a vet for diagnosis and treatment.