Cause of numbness in one heel?

Nerve compression. Numbness can be associated with nerve injuries. This may be due to swelling in the heel or traction of the nerve caused by lack of support for your foot. The nerve in question is a branch of the tibial nerve. Just like carpal tunnel syndrome in the wrist, you can get entrapment of the tibial nerve in the ankle. You probably just need support in your arch so get superfeet supports or see doc.