What Causes A Sharp Pain In The Shin Bone?

Hi, A few weeks ago I fell over and came down heavily on my right knee catching the edge of a raised piece of half inch boarding. A couple of days later I experienced a very sharp pain at the top of my shin bone below the knee joint - this is area is very sensitive to touch and I've now noticed my calf muscle is numb to touch. Could I have chipped a bone? I'm aged 56 and weigh 250 pounds.