Sharp Pain Underneath Right Armpit After Several Days Of Extensive

sharp pain underneath right armpit after several days of extensive coughing due to bronchitis. Was seen by a doctor for the bronchitis and had a CT scan w/contrast before the pain started to rule out PE (I was extremely short of breath).

Is this likely a pulled muscle or ligament? Extremely painful. Can it be treated with heat or cold, or merely painkillers?

Thank you