So... technically, I really AM asking for a friend. She's been running with a forefoot strike for close to a year. Short runs, building up very slowly. She wears shoes (as opposed to sandals or five-fingers). She says the shoes are plenty roomy enough. Recently after a short run (2 miles), she noticed tenderness when she pressed down on the second toenail of one foot. A couple days later, there is a dark bruising color under the toenail. Pressing down on the toenail produces a sharp pain (as opposed to a sort of dull ache). She did a 6 miles run (which is her long run at this time) about 2 days before this short run, but came back pain-free from the long run. She did switch socks recently, and they have a thick seam that does cut horizontally across the toenails and she says they were kind of tight. Is it possible that this seam is just pressing down too tight and causing the injury?