Tip - Ask the Doctor: Should I Be Concerned About Sudden Numbness in my Foot?

Q: I am a runner, and have recently noticed numbing on my outer left foot in the area immediately under the ankle bone. It's been this way for a couple of days. There is no pain involved - only mild discomfort. It is only isolated to this one area. Should I be concerned? How long might this last? I don't want to put my running regiment on hold (20-30 miles/week) unless absolutely necessary. How long should I wait before seeing a doctor?- Kathy, California