Hi Jane,
Have you been to see anyone about the condition? To make sure there is no other pathology such as referred pain from the spine or the hip.
If the problem is caused by the tarsal tunnel area it could be a case of poor range of motion at the ankle or stiff muscles and tendons in the area. The tarsal tunnel is close to the flexor halluces longus tendon and the tibialis posterior tendon which, if stiff, could be increasing your symptoms. I would look into the function of the ankle first. Therefore any exercises you need would depend on what was found. I'm not sure any supplements are going to help long-term especially if NSAIDs are not having any effect.
Do you perform much exercise?
Hope this helps
Ben