It could be the track itself. All the turning on the track can place stresses on your body. First, rest and treat the injury so it doesn't become more severe. Second, if you don't have access to roads, trails, or other places that don't always have you turning the same direction, reverse directions on the track. For example, if you're running for 2 hours, maybe you would go 30 minutes in a counterclockwise direction, then 30 minutes in a clockwise direction and continue to alternate until finished.