A 55 year-old male was brought to your emergency department by EMS, after falling down 13 stairs. He is alert and oriented, and is complaining of chest pain. His initial vital signs are: 37.5 C, BP 88/45, HR 123, O2 95% on a non-rebreather. His initial portable chest X-ray shows a left sided pneumothorax that is 10% in size. What is your next step?