This is Dr Basu, Experienced Specialist.
I am here to address your concerns and provide great service.
Coughnig uses all the muscles of the ribcage.
So the muscles at the left breast area also will be affected with coughing.
Most likely you have inflammation of the rib cartilage at the area and that can get aggravated with coughing.
Now given the location, heart relatd problem also possible.
However, this causes symptoms like shortnessof breath with exertion as well.
Also any charcoal dust related inflammation of the lungs
will cause persistent coughing and shortness of breath.
Yes you do need to see your doctor for EKG, chest xrays.
However, your problem is mostl ikely rib cartilage relaetd and should improve with NSAIDs like Ibuprofen 600 mg 3 times daily.
Steroid injection also at the area will be beneficial in more resistant symptoms.
It was my pleasure to help you today.
If I have answered all your questions, Please click on Excellent service so that the website allows me to assist you further :)