Causes would inlcude: circulation problems (do you often have cold feet/toes? any discoloration of your feet? ), Or maybe there was an injury to your foot/bruising.
This is most common in runners or very active people. Most likely the cause is nerves having too much pressure on them, or commonly called compressed nerves.
This could be a number of things such as diabetes or something even more serious. You might want to contact your doctors off and explain what is going on.
Possible Causes could be: Poorly-fitting shoes, Poor Posture, A Variety of Medical Conditions (e.g., arthritis, diabetes, muscle and motor control-affecting diseases) and strenuous exercise.
