There is right chest wall subcutaneous emphysema.
The initial right shoulder x-ray was performed to look for fracture around the right shoulder in this patient. The presence of sc emphysema led to a chest x-ray which revealed right sided rib fractures and a small pneumothorax.
Pay attention to soft tissue signs on a shoulder x-ray. A trauma patient with air in the chest wall should be imaged further to rule out rib fractures/aerodigestive tract injury.