Sudden chronic cough--caused by self induced coughing?

Yesterday, I had a normal cold. I was coughing up yellow phlegm and blowing out clear. So I was like, let's help this along, because I had this same cold a month ago and it just would not go away. So I forced myself to cough and now I can't stop coughing! It's a very dry cough and I cough every 5 minutes for about 30 seconds non-stop. How do I stop without using a cough syrup?