I would say keep an eye on him and watch for any other signs of a problem. Is his nostrils clear and his vents? Also have you checked his mouth for mucus? Any sign of him blowing bubbles? If you have not noticed any signs of a respitory infection I would say just kick up the heat some and that should do it.
What are your currnet temps at on the hot and cool side now? Also what is the snake being housed in?