Phil,
If the pain is UNDER the heel bone and painful to walk on it may be inflammation in the broad band of tissue that keeps the 'arch' of the foot in shape, where it joins the heel bone. Known as 'plantar fasciitis'. Best way to treat this is with a steroid injection in the tender spot. Alternatives are: 1. Do nothing, chance it may go on its own. 2. Ibuprofen or similar.
If the pain is in the Achilles tendon where it joins the heel bone, and painful on moving the foot up and down, it may be an inflamed Achilles tendon and its sheath. Rest, physio and Ibuprofen may help. Look for any aggravating factors (other than driving your car) to stop.
Malcolm