Back when I was in the Navy, I learned that I my feet could increase a whole size by the end of a long day. After Sept. 11, 2001, I was doing 18 hour static gate guard shifts with 12 hours of standing in basically one spot. After a few hours, our feet would get hot and one of us at the gate would take a couple minute break in the shack during which we'd lay on the floor, feet up against the wall, and after a minute, one could feel their boots loosen up and almost fall onto their legs.
Fast forward 18 years, no longer in the Navy, and a very active cyclist but in spite of my daily cycling, I was diagnosed with a 3 foot blood clot from my ankle to my groin during a visit to my GP. After a few months of blood thinners, a break from the bike with only walking, I was good to go (cycling is fine with thrombosis, but Philly is a dangerous city with regard to traffic, and getting hit while on blood thinners can be rapidly fatal.) That said, I have to wear compression socks full time. If a doc recommends compression socks for varicose veins, it's due to venous insufficiency in pumping the blood back to your heart, so it pools and will eventually thicken. The compression socks relieve the itching and pain from varicose veins, and they support blood flow back up to the trunk.
Be careful with the compression sleeves that don't have a foot to them. The foot/ankle joint is where a lot of clots form and the band around the bottom of the sleeve can actually hasten the formation of a clot. They may be good for folks who don't have venous insufficiency, but if your feet are swelling that much, they may only increase the swelling. Regardless, see your doc. Pay very close attention to pinching feeling behind your knee, and observe asymmetry between the size, color and shape of your calves. When you get home, lay down and raise your legs so your feet are at least 6" above the level of your chest, the higher the better, while remaining comfortable.
Also, the pain in the ball of the foot may be exacerbated by flexible sole shoes, which are making your foot work harder wrapping around the pedals. Try to find some stiffer sole shoes or have a cobbler reinforce the sole with something to make them more like a cycling shoe.