[724Skinsfan]

That sucks, man. Rest it, stay off your feet as much as you can, take some ibuprofen a couple times a day if your okay with it, ice it if starts to get inflamed. If you start running again, once it's gone, think about investing in a new pair of running shoes. Also, if you're running on concrete sidewalks you may want to find a different terrain type. If that's easier said than done then try shortening your stride and landing more mid-foot rather than heel striking.