A 28-year-old male presents to the emergency department with acute onset dyspnea and left-sided pleuritic chest pain following a spontaneous pneumothorax. A chest X-ray (CXR) shows a 2 cm pneumothorax with no mediastinal shift. The patient is hemodynamically stable, oxygen saturation is 94% on room air, and respiratory rate is 22/min. What is the most appropriate immediate management?