Place a small soft ball on the floor. The ball should be slightly larger and softer than a tennis ball.
Lower yourself onto the small soft ball, about one to two inches outside of your belly button, near the area that hurts. You will feel a slight discomfort as you lower yourself, this is your psoas responding to the pressure.
Come up on your elbows and arch your back. This action will cause a more forceful stretch and, in turn, will cause your psaos to release.