Hullo and welcome to Jazz and Banjo. Gorgeous little dog. As Greys said re desexing. All the dogs I've had have gradually shrunk away to nothing - their nuts that is, not the dogs.
You may need to get an Elizabethan collar to put around his neck if he won't stop licking. Natural thing for a dog to do to try to heal a wound, but not good for the wound in this case.
We need a better photo and weight and height to make any guesses as to mix. If he has Pappillon, you are in for a treat. They are such great little dogs.