You may be suffering from the shock of your injury. Are you scared normally after you're injured? If you are, your blood pressure may drop, causing you to have blackouts. But i'm not a doctor. I suggest seeing your doctor and see what he/she has to say. Wish you the best of luck. I hope I helped you a little. =d

My suggestion to you is to get a physical and talk to your Dr. About what is going on, it might be something that is fixable with meds and what not such as oxygen, it could be a post -tramatic syndrome but you should get it chcked out.
Good luck!