Instep Pain

I have terrible pain in my right instep, which radiates to the ball of my foot, and in between my big toe and 2nd toe.
I DO walk on concrete and tile floors for seven hours a day, Mon – Fri., but the pain continues through the weekend also.
I’ve even begun to limp from it.
I know you can’t make a formal diagnosis over the computer, but what does it sound like, and what products can I use to relieve the pain until I can see a podiatrist?
I’d appreciate your help.