A 32-year-old man presents to the emergency department 2 hours after sustaining a stab wound to the left anterior chest wall at the 5th intercostal space, mid-axillary line. He is haemodynamically stable with a respiratory rate of 18/min and oxygen saturation of 98% on room air. There is a small amount of blood-stained fluid around the wound. On examination, breath sounds are equal bilaterally and there is no subcutaneous emphysema. What is the most appropriate next step in management?