I have quite severe pain in lower left leg and side of left foot. i am trying to determine whether it might be varicose vein or something else. there is selling of something just under surface but i can't tell if it is vein or tendon.?

See MD : There is no way to know what is causing the pain without more information and examining the leg. I suggest you see your doctor to get an accurate diagnosis and treatment.

Unfortunately,: You did not state if it was the inner or outer side of the leg and foot. I will assume for the time being it is the innerside. So you correct it could be a vein or a tendon. The great saphenous vein or the posterior tibial tendon. Try applying warm compresses and take an antiinflammatory, elevate the leg. If you have a flatfoot, wear an arch support. If you don't improve - goto doctor.

Not a vein: Veins usually don't cause pain at the foot (possible but not likely). See a podiatrist. Yo may have a cyst there.