A 28-year-old man is brought to the emergency department with a gunshot wound to the right chest (4th intercostal space, mid-axillary line). He is alert, respiratory rate 24/min, oxygen saturation 94% on room air, blood pressure 118/76 mmHg, and heart rate 102/min. Breath sounds are diminished on the right. Chest X-ray shows a small right pneumothorax (< 2 cm at the hilum) with no haemothorax. What is the most appropriate next step?