When this occurs, the foot becomes very swollen and often has a wider appearance of the heel compared to the uninjured foot. This bone is very vascular so when it breaks, you are going to see a lot of bruising. The bruising usually surrounds the heel bone, which is a class sign of a calcaneal fracture. It is often too painful to apply pressure to the heel and by the way it feels "you know you've done something bad"!
Best thing you can do is get off the foot, put ice on it immediately and call our office right away. If it is after hours or on the weekend, get yourself to the ER. Small breaks that are not dislocated often heal well with immobilization like a boot or a cast. But significant breaks usually need surgery to put the bone back together and reduce the chances of severe arthritis in the future.
These things hurt...a lot. But left untreated, can result in severe, debilitating arthritis down the road.