I figured there might be a small flare, this is very common in many "sprinters" but my other concern as well is that you could very well be that you are not using your shoulders when you run. The running motion of a sprint includes swinging shoulders. Try another mini sprint and notice the movement of your arms in the mirror (side view). At the bottom portion of your arm swing, your arms should still be at 45 degrees (from bicep to hand) and near the top, maybe 10-15 degrees at most. What I'm trying to say is, use your shoulder to swing your arms back, don't just extend your arms. Not only will this save you from any nagging injuries, but in the long run will make you a more efficent sprinter and therefore faster.
Don't hesitate to ask any questions.