Why could my dog be coughing?

For over 24 hours now, my dog has had a cough. It's not a wheezing coughing like it would be if it were kennel cough, but a cough that would be similar to if a person inhaled water or food and was coughing (or trying to cough) it up. He is a chesapeake bay retriever, full grown at two years old, and has never had any health problems before. This has not affected his personality at all, he still acts the same and has the same energy he had before, I just feel useless in the sense that I don't know how to help this cough. My first thought was that he may have inhaled something, but I think that he may have coughed it up if he had.. What else could make him cough? Is there a way to help him or should I take him to the veterinarian?