A few days after my first marathon last year, my right foot swelled up. Massively. I took a couple days off, and did (relatively) short runs. The foot hurt and would swell up like a baloon. I self-diagnosed as having a stress injury (fracture?) and accepted I may have to stop running for the rest of the year. I was able to get an appointment with a sports orthopedist at MGH, and he prescribed physical therapy. X-Rays showed no (remaining) fractures.