This is a case of varicose veins.
If left untreated, varicose veins might lead to blood clots in future- known as deep vein thrombosis.
Next Steps
Consult a vascular or general surgeon.
Till then, keep the legs elevated over pillows while lying down and over a footstool while sitting. Do not let the legs hang for long periods of time.
Avoid standing and walking for long periods.
Apply appropriate sized compression stockings.