Hello! Thank you for the query. Such lump has appeared due to blood clot in the vein or due to vein burst. Blood clot usually causes the area hard and tender. It appears in the place where varicose vein is usually present. Vein burst lump is less painful and not very hard. Both issues indicate chronic veins insufficiency. This condition can lead to veins thrombosis which in some cases can be life threatening. That is why I suggest you to have Dopplers veins ultrasound done and consult a surgeon. In a meanwhile, to prevent such situation, you should wear compression stockings. Hope this will help. Regards.