I have a sharp heel pain on both feet right where the big part of the heel bone starts. what could it be?

Heel spur: Could be a heel spur, does it hurt more in the morning and after standing if you had been sitting for a while, then it probally is. See your local foot doc foran accurate diagnosis.

Plantar fasciitis.: The most common cause of heel pain is plantar fasciitis: an inflammation of a thick band of tissue that helps hold up the arch of your foot. It attaches to your heel bone, and is usually the most painful for the first few steps in the morning, or after sitting a long time and then standing quickly. See a podiatrist to rule out stress fracture or nerve entrapment.