My brother in law hit his shin on a concrete step.  A huge knot popped up.  We put ice on it and it was down the next day.  There is a sore about the size of a quarter where he hit it.  We have treated the sore with medi-honey, and there is no fever.  However the entire shin from the site about 12 inches down is red.  No fever.  He is diabetic with congestive heart failure.
Welcome to Chat Doctor .1. The symptoms seem like an infective feature.2. With underlying medical conditions like diabetes and cardiac pathology, I would recommend seeing the GP and let it get examined. 3. As in diabetics possibilities of infection are more.4. Muscle relaxant, and a course of antibiotic is what he needs according to me.5. But one needs to examine the area only then come to conclusion. Hope it helps you. Wish you a good health. Anything to ask ? Do not hesitate. Thank you.