In reply to Welsh Kate:
Welsh Kate has the best suggestion,
I had the problem a while back now , the GP diagnosed it correclty and suggested steriod injections, they worked for the right foot but not the left, I also tried a foot splin ovver night but this was very uncomfortable.
Then by a chance conversation with a podiatrist they suggested the use of orthaheels which worked a treat, within a few weeks the pain had vanished.
Now I use the insoles in all my shoes, trainers etc but not my walking boots (Scarpa Rebel Lites) they didn't feel right and gave me some odd aches in my inner quads which I linked to the insole causing possibly superination but that is just a trial and error diagnosis.
All in all would suggest seeing a specialist
Pban