If it hurts under your heel, you may have one or more conditions that inflame the tissues on the bottom of your foot:
If you have pain behind your heel, you may have inflamed the area where the Achilles tendon inserts into the heel bone (retrocalcaneal bursitis). People often get this by running too much or wearing shoes that rub or cut into the back of the heel. Pain behind the heel may build slowly over time, causing the skin to thicken, get red and swell. You might develop a bump on the back of your heel that feels tender and warm to the touch. The pain flares up when you first start an activity after resting. It often hurts too much to wear normal shoes. You may need an X-ray to see if you also have a bone spur.
Treatment includes resting from the activities that caused the problem, doing certain stretching exercises, using pain medication and wearing open back shoes.