Heel Pain

[Gadgetier]

Hi,

I've recently had a pain at the back of my heel which I don't understand.
When touching my toes there is no pain however, when in this position I lift my big toe I get a sharp pain in the back of my heel, almost central of the Calcaneus bone.
Having damaged my Achillies on the other leg I don't believe it's that but with a couple of half marathons and a full marathon on the horizon I'm concerned as to what it is.
I would appreciate any ideas

Cheers

Gadg