You need to take him to the vet before it gets really serious. I would not wait one more day.
Here is some info on it I got off the web.
Sounds like kennel cough. Here's some more info: " Kennel cough is a highly contagious upper respiratory infection that often affects animals that are kept in a confined space such as boarding kennels, dog shows or veterinary hospitals.
Symptoms include a persistent dry hacking cough or bouts of deep harsh coughing often followed by gagging, which may produce a foamy mucus.
What is the conventional treatment?
Mild cases may improve without treatment. Conventional treatment of kennel cough often involves antibiotics which tend to relieve the animal's symptoms fairly quickly, but also have a general weakening effect on their immune system, which can cause further problems, especially in the long-term.
Vaccinations to prevent kennel cough are also often recommended. But research indicates that frequent vaccination or over-vaccination may unnecessarily stress a pet's immune system. "