Mystery Recovery

So my foot hurt really bad all day yesterday.  As soon as I got home I tried to keep it elevated.  I even slept that way.  This morning, the pain had reduced by about 90%.  By midday it was almost gone.  Every once in a while I'll start walking a little too fast and I'll feel a slight twinge of pain but that doesn't happen too often.  I have no idea what this could have been.  It apparently was not anything broken or pulled or strained because those things don't go away overnight.  Circulation problem maybe?