What to do if i have heel pain on the bottom of my heel what's wrong?

See a podiatrist: You could have a heel spur, injury, plantar fasciitis.

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 doctor to rule out stress fracture or entrapped nerve.