Thankfully this condition didn’t last long and I put it down to wearing wellington boots on a particularly long dog-walk.
I can only describe the feeling as ‘sunburn’ and at first I thought I had ‘rubbed’ the inside of my ankle/foot with repetitive irritation against the boot liner. There was nothing visible around my ankle but trying to go onto tip-toe or run upstairs reproduced the burning pain. The reason for the pain was an again due to my feet or specifically hind/rear foot rolling inwards inside the unsupportive wellington designed more for stable yards than undulating muddy terrain. As a consequence I was overusing the main tendon Tibialis posterior, that runs from its muscle in the inner calf and joins with a bone on the inside of the foot and branches underneath the foot to prevent the foot from pronating (rolling inwards).
Swapping back into Chelsea/dealer style ankle boots with specific high supportive style insoles inside, helped settled the discomfort within a few days.