I am having pain in top part of foot no swelling but big toes is cold feeling I can only walk on side of foot is this serious and what is causing it?

Could be. This could be serious. While this could be an issue of dropped arch or inappropriate shoe wear, you may have a fracture, or even a vascular issue. This should be evaluated by your family physician.
Yes. You need to see a doctor immediately, there could be a circulation problem.