I've been experiencing the same thing. Kind of left center heel. Not sure what it is other then an anomaly. Maybe stepped on something wrong and didn't know it. I have an issue with my left foot where it gets stiff and achey after laying down for awhile. At 35 some would say I'm getting old but i refuse to go along with that. I know the foot is very intricate and as tough as the foot is, the slightest tweak can linger for a long time. Pop some ibuprofen, stretch the foot out and hike on. Happy trails to your Whitney hike. I'm due up therr beginning of October and can't wait!
