Several poss. Causes. Heel pain can come from a mild injury, such as jumping off a fence. It can come from overuse, such as hiking 5 miles when one is not a hiker. There can be irritation/inflammation of the arch area of the foot, or at the achilles' tendon from the calf, both of which are connected to the heel. Sometimes there is a bony heel spur at the bottom. A primary care, orthopedic, or podiatry doctor can help.
Interference field. If pain in one side this is due to disruption on energy either due to scar or trauma in body esp midline like c-sect or episiotomy if it is bilateral systemic could be B12 deficiency.