Do you know anything about veins that cause pain and bruises?

This is a new one for me….yesterday I was doing some things in my back yard when I felt a pain on the sole of my foot ( I was wearing sandals at the time). I sat down and looked at the bottom of my foot and there was a bulging vein where the pain was. It was quite tender to touch and a little tender to walk on after that. I tried to stay off it as much as possible for a while and kept it elevated when I was sitting. I checked it a few times and about 3 hours later it had become a bruise, no more bulging vein. Where did it come from and where did it go?