Symptoms of heel pain
NHS Choices Medical Reference
Pain usually starts gradually without any injury to the area. Often it is triggered by wearing a flat shoe (e.g. flip flops on summer holidays). This stretches the plantar fascia too far and begins the inflammation of the area. Typically, pain is felt under the foot towards the front of the heel. It is common for it to start in one heel only and normally it is most painful when standing up first thing in the morning.
It can often ease with activity but then become more pronounced at the end of the day, or after a long time spent on your feet.