Basically, the blood in your veins, as opposed to your arterial vessels, are low pressure. You have these little valves in your veins that catch blood as muscle contraction moves blood upwards.
A faulty valve means that the valves aren't closing completely and therefore blood will pool in the vein since it is having a hard time traveling towards the heart. When blood pools, the vein distends, and that is visually what you see in a varicose vein, stretching/bloating.
As far as pain in the area...I'm no so sure if that is related to the vein. It could be, but veins are relatively superficial and soft, so I don't imagine inward distention would irritate deeper tissue. However, general edema (swelling) in the area increases pressure on local tissues, that may be causing pain. What there any sort of recent trauma on that part of your leg?
The swelling in your foot, the same side as the varicose vein, implies a lack of sufficient blood flow in the area. That could occur for many reasons though.
There are ways to enhance venous return, you can sit on the floor and put you legs up on the wall.
However, this isn't medical advice and there is the possibility for contraindication because blood clots can form in varicosities due to a lack of blood movement. Freeing a blood clot into your cardiovascular system can be dangerous.
But, you're likely an active person, so it shouldn't be much of a concern, but I would get it checked out to be sure. Varicose veins are common and there is well established medical protocol for those kinds of things.
A little more insight -
the most common vein to become varicose Great saphenous vein - Wikipedia, the free encyclopedia