A 62-year-old woman undergoes elective tracheostomy for severe bilateral vocal cord paralysis secondary to thyroid cancer surgery performed 8 weeks ago. The procedure is completed uneventfully under local anesthesia. On postoperative day 2, the patient develops sudden onset of subcutaneous emphysema over the anterior neck and upper chest, with mild dyspnea. Chest X-ray shows air tracking into the mediastinum. The tracheostomy tube is in situ and patent, with good air entry bilaterally. What is the most likely complication and the most appropriate next step?