I have a varicose vein in my leg, now ive discovered a pea sized lump (not movable) under my skin where the varicose vein is. Tumor?? so scared

Phlebitis. You may have developed a clot in a varicose vein and this is called superficial phlebitis. This is not dangerous and the treatment consists of heat and ibuprofen. See a vein specialist.
Keep an eye on it. I would not worry about it right now. But do check it once weekly and monitor its size. Unless it grows bigger over the next 1-2 months, it is unlikely to be a serious matter. I suspect it is a small clot of blood which should subside in a month or two. If it does not get smaller or if it grows bigger, get it checked by your doctor..
Veins and lumps. Varicose veins are dilated veins...up to where you can feel them easily. This also allows you to feel the valves that are part of the veins normal structure. Pull up some pics of vein anatomy to reassure yourself.