Pain under the heel is known as Plantar Fasciitis, and can come on after excessive amounts of walking - or even after wearing different footwear. It is more prevalent in the older athletic person and can be quite persistent once it starts.

It can be caused by inappropriate footwear, quite often tight calf muscles and pronated or flat feet.

It is important to keep off the foot as much as possible initially and keep the calf flexible by pulling the foot upwards. Your Doctor may prescribe anti-inflammatories and sometimes an orthotic (like an arch support) can take the strain off the Fascia and encourage it to heal.