I find this happens in my right foot about 2-3 miles in as well - left leg/foot feels totally fine but pain on he inside of the right calve (above the ankle) and numbness across the top of my right foot. I'm really trying to stretch out well both during and after a run but still this pain persists in about 90% of my runs! so frustrating as I end up going at a snails pace due to the pain! I echo what everyone else has said, if anyone find out what it is please post on here!