Poked into muscle contusions some more online and found some scary articles about myositis ossificans (essentially, formation of bone tissue in sufficiently traumatised muscle) in the wake of muscle contusions resulting from traumatic injury and about quadriceps contusions generally (
http://www.hughston.com/hha/a.quad.htm is the quicker read of the two relevant articles I found). Now have an appointment to see my doctor, though for Tuesday rather than Monday. Will stick as far as I can to exercise that doesn't cause pain until then. I may try some test cycling this evening, free of any need to actually get somewhere. I worry that I won't get enough volume of cross training in to avoid gaining weight if I can't manage cycling soon.