This is a suggestion, but not a diagnoses. What kind of heat do you have? Perhaps the air in your home is too dry. Try using a humidifier, or if you have a wood stove, put a pot of water on the stove-to add some humidity to the air. If he has no other signs of illness, this may help. He may even have a sore throat. If he has not allergies, you could give him a little honey. If it continues I would seek vet.