You are 15 or 16 years old, more than likely you are growing rapidly, many kids your age experience pain in the joints (knees, hips, elbows), as you are growing. Take it easy, if the pain persists, see a doctor. This quest to be a D1 player is a “marathon” not a sprint, you still have miles to go. Pace your self, you are still 3 to 5 years away from D1. Stay healthy, work hard and have fun!