What the H did I do to myself?

A few days ago, I went for a good hard run. It was an interval, with super short runs, so I decided to try out some speed stuff. 2 min run, 1 min walk, 12x, which is about half the total time I normally run. I gradually built the run speed up over the whole thing, getting faster each time (I made it back home a full two minutes faster than I went out!). I peaked at going absolutely all-out, unable to move faster or keep running past two minutes. Absolutely no pain while running, just good hard breathing, good happy-hard-working muscles.

Then, I dared to take off my shoes. Wow, what a mistake! Pain shot up the outside of my foot and lower leg. It moved around, but was so sharp it was at times knee-buckling. Though the pain moved a bunch, as I said, it always started/centered where my fifth metatarsal sticks out just below my ankle. Mine sticks waaaaay out, to the point it has caused issues in the past but I don't remember this ever happening before. It kinda felt like it needed to pop/crack, like you pop your ankle.

Fast forward a few days, and the pain has settled right around that fifth metatarsal, and is now more constant but not nearly as intense. But, here's the weirdest part, it is now in BOTH feet, in the symmetrically-same spot.

There is no bruising, no significant swelling, and is slightly warm to the touch, but not hot. Wearing tight shoes sorta helps a bit, and is markedly better than going barefoot. I'm stumped on this one. I've seen the doctor way too much recently, so if it is something simple that I can stretch, heat or ice, and stay off of, I'd like to avoid that trip.

Any ideas?