Boston marathon and a MRI

What would training be without an injury or setback. I have had a very mild discomfort on the ball of my right foot that has gradually progressed. Nothing on top but the dreaded stress fx thought has entered my mind. It seemed to have started after a longish run in the Brooks Ghost. I got them thinking that they were a compromise between the minimal Launch and the maximally cushioned Glycerin. Were the Launches causing a problem? no. The Ghost have a little more arch. I think they pushed my foot to supinate a little more. For most part I am a neutral midfoot striker. Anyway, a little tenderness started after the long run and has progressed. I ran the Gasparilla relay in the Glycerins for 19miles with essentially no problems. I have been running in them a little more trying to stretch out the Lauches for the last 100miles. I ran the Sarasota half in the Launches without much problem. Last weekend I developed pain in my right foot at the end of the run. Much like muscle spasm. We did 20 miles a week early just because it was only a little further than 17.3 miles and the weather was good? It did provide for good psychological reinforcement for Joules 2 and 3 that they still had a 20 miler in them. Nevertheless, the nagging pain has persisted. Worse after a run then during. No pain on top with minimal pain with running. Because Joule 3 is a radiologist I was privileged to get a peek at the injury with an MRI. No breaks just bruising around the second metatarsal joint. That was a relied. I figured I was going to run anyway but would drastically taper if there was evidence of a stress fracture. It is Boston. I think I will stick with the Lauches and break out the new ones for the taper and race. The Ghost will sit idle and the Glycerins?