Help with Toe/Foot Pain

I am currently doing a Nordik Track stepper and was up to about 40 minutes when out of the blue, I go this burning at the top of my right foot around my two babie toes.  It kept burning as long as I was stepping.  It doesnt happen when I walk or anyother time.  I decided to give it a few weeks to heal and try again.  Well sure enough, after 15 minutes the burning starts again.   Does anyone have any idea why or what I can do to stop it?  The stepper is my main form of exercise and I love it.  I do not want to give it up, but I cant work through the burn as it is really, really bad.   Thanks for your input - I really need suggestions. Mumma