I think you should see a doctor ASAP... RSD affects calcium in the bones, and a stress fracture is possible because of that. A broken foot bone can be very painful.

Also there are lots of nerves on the top of the foot... these can get compressed if you wear shoes what are tight in that area or laced to tightly.

There is a nice new lotion out... called Aspercreme with Lidocaine.
You can rub some on the area and if this is just a compressed nerve, it will numb it for most of a day. It is as strong but OTC and not expensive, as the compounded RX lidocaine creams.

But if you have a broken foot bone, you'll need a podiatrist or orthopedic doctor to immobilize the foot so it can heal.

Get your Vitamin D checked, so that you can absorb calcium from food properly, as calcium is necessary for healing broken bone. Also consider Vitamin C 500mg-1000mg a day to see if that helps. Vit C has shown in some European studies that it prevents RSD in patients with injury or surgery to the feet and ankles.