Foot Pain (25 days until NYC) - suggestions?

I don't want to panic, but have a foot problem which began during a short fun last night. Had a good training week last week (35 miles) with an 18 miler on Saturday. Felt fine the entire time, took Sunday and Monday off and continued to feel good. Started a 5 mile run last night and began to have significant pain on the outside bottom of my right foot (not a doctor, but it seems like it is just in front of the heel bone). Pain continued to get worse while running. Stopped immediately when I stopped running. And then lasted the rest of the night anytime I would apply pressure with my foot flat.

I was initially concerned with a stress fracture, but have no swelling or pain to the touch. Today my foot is a little sore to walk, but did an easy 1.5 miles at lunch and the pain would come and go. It never got as bad as it was last night, and did not increase after the run like it did last night.

Any thoughts or suggestions? This is supposed to be my largest building week before beginning to taper for the NYC marathon. I have 10 miles on the calendar today, but am a little scared to push it until I can figure out what is going on. I guess I am most interested in ruling out any type of stress fracture.

Any advice/suggestions would be greatly appreciated.