Tendonitis

I think I may be developing Tendonitis.  I have pain on the top, outside edge of my left foot.  It started a few weeks ago, right around the time I discovered that walking on an incline burns far more calories than walking on a flat surface.

I haven't been running on it in order to rest it but I have still been walking at least a mile a day (still on an incline).  It seems like it might be getting worse.

I miss running and I really need the stress release.  Do I just run through it?