You may be describing what’s called a “pump bump” or Haglund’s deformity. It’s caused by repeated friction of the Achilles’ tendon where it attaches to the bone. Usually, patients with Haglund’s deformity report heel pain and swelling.
An X-ray will show bone growth on the back and upper portion of the calcaneus (heel bone). Calcium deposits may be seen in the Achilles tendon at the place where it inserts into the bone.
Treatment is often by conservative means such as a change in shoe wear, using a heel lift, and/or steroid injections. Nonsteroidal antiinflammatory drugs (NSAIDs) are usually prescribed. If the symptoms aren’t changed by these management techniques, then surgery may be needed. The surgeon will remove the bone spur and debride (clean out) the Achilles’ tendon.
There could be other causes for your current symptoms. A medical exam is really needed to know for sure. Even if it is not painful or bothering you, a baseline X-ray to show your current status may be helpful later.