Big vein below right calf. is there any treatment for that?

Varicose veins: Yes. Many treatments available. Call your doctor. Also in additioncompression hose, and avoid prolonged standing, to avoid worsening.

Get evaluation: Most likely is a varicose vein. You need to see a vein specialist (phlebologist).

Need Ultrasound: Yes, you need an ultrasound of the superficial and deep veins in your legs looking for venous insufficiency. Seek out a local vascular surgeon.

Need venous sonogram: You seem to be describing a varicose vein. Varicose veins are caused by leaking valves(reflux) usually in the saphenous system which are the feeding veins to the varicose veins. A venous reflux sonogram will identify the refluxing valves and help to determine the appropriate treatment. If the valves leak, then you would be a candidate for laser or radio frequency closure.