I have had left foot pain that has progressed over the past 3 weeks. When I look at my foot now there is a lump on it below the toes. It lies below but in between my big toe and second toe. It's tender and discolored a bit. It's about mid foot. Any idea w

Bruise. May have possible stress fracture. My advice would be to seek medical attention ASAP.
Foot pain. with a lump should be examined by a doctor.
Mass or Mess. I'm afraid that this is one of those conditions that has to be physically examined to be able to make a call. It certainly sounds like soft tissue but actually feeling it is essential. One needs to distinguish as to it being an actual mass of the effects of bruising. You will have to consult with a specialist for the most reasonable solution.