Suggest Treatment For Severe Cough Accompanied By Pain In The Chest

I am 25 years old and have been coughing for about 4 weeks now with no other symptoms. I did have a cold for the first few days at the start (4 weeks ago) but that has gone but kept the cough. For going on 2 days now I have a stabbing pain in my right side/back area when I cough, laugh, lay that way, or touch. What could it be?