Hi Jenkins. How's your foot pain? Is it better, worse or same? When you run or walk on it, how bad is the pain out of 10 (where 0=no pain and 10=maximum pain). Can you walk on your toes? It's hard for me to say what you got but the only recent change to your training program is the increase of running distance so its making me to think possible bone bruising/ stress fracture of 5th metatarsal? You might want to see your doctor for an X ray of your foot for possible fracture. You should rest and once the pain is better then try gradual return to walking/ running. Good luck and hope you get better!