This sounds like musculoskeletal pain. You should continue to take the antibiotic until it is gone. Also you should avoid heavy lifting. When you cough hold your chest so that it hurts less. You should gradually feel better. If you do not, check with your doctor.
Could be costochondritis. It's inflammation of the cartilage that connects each rib to the sternum. It can be very painful. It's brought about by trauma or strain to your ribs. It's benign and usually resolves itself after a while. The main symptom is pain in the associated area. Usually it is between the second and third ribs, but it can be elsewhere. Very tender to touch and the pain is associated with coughing, sneezing, heavy breathing, and can sometimes occur in more than one spot at the same time. Usually for it to resolve itself takes some time. Avoid heavy lifting and strenuous exercises and, if you can tolerate it, treat with simple painkillers like NSAIDs. But, like always, you should visit your doctor for him to confirm or veto any ideas on your predicament.