Many people falsely believe that a dog's nose should always be cold and wet, but this is seldom the case. After sleeping or resting, a dog quite often will have a warm and dry nose. If however, a dog has a warm and dry nose over a long period of time, this very well could indicate your dog has some health problems. In this case, it's best to take your dog to your local vet and let him determine if there is a problem.
More often than not, the best gauge of your dog's health is your common sense. If your dog is normally playful and loves playing tug-of-war and other games with you and is acting lethargic, more than likely something is wrong with him and a visit to the vet may be required. Dogs are like humans in that when they run a temperature, it can be felt in their bodies. If your dog feels hot to the touch, it is very likely they are running a fever and you will need to take action of some sort to nurse them back to health.
It's a common fallacy that a dog with a warm nose is sick in most cases. Use your knowledge of your pet and your common sense to keep your best friend in good health so you can enjoy their company for many, many years to come.