Dogs can just get hoarse. Is there any possibility that he's been really yelling when you've been gone? I've definitely noticed it after a puppy's screeched all night or when a new dog thought she had to bark all day long at imaginary dangers.
It CAN be a symptom, just like a human's hoarseness can. But it's a bad sign (of kennel cough, cancer, etc.) just about as often as it is in humans--in other words, barring any other symptoms, and as long as he stays happy and healthy acting, I'd let it go for a couple of days before worrying. If it gets much worse, or he starts coughing a ton, then think about escalating your concern.