As a defense mechanism, chams are designed to just let go and free fall onto the leaves etc below, and run off. They are built as bags of air with springy cartilage sides. But they are not meant to fall onto concrete etc. I have no clue if they broke a rib or not, but most of the time ANY trauma causes black spots. Its a hair trigger. You holding firmly with your hand to give meds might cause a black spot. its not really a bruise, its "the skin got roughed up" like a human getting a scratch mark, so its not even classified as trauma. Its not blood pooling to the surface from broken capillaries like us humans. It should go a way in a week or 2.
