I, too, have problems with my left foot. It is due to a surgery that was fairly invasive for a hemiangioma tumor wrapped around the tendons of the instep.

Mine swells up periodically, throbs now almost every night, and
this week, my calf swelled up too!

I do two things for it.. Salonpas patches, and magnesium lotion.
I do notice that stairs seem to make it worse. UpNorth where there are no stairs to speak of (only 2 gentle porch ones), it tends to not swell. Here at home, is another story.
Chairs do not help, and tend to make it worse.

For veins, if you suspect a vein issue, try taking some grapeseed extract. This really helps with leg veins. I stood for 40+ yrs! But yours may be due to inflammatory changes in lymph return to the veins. That is what I think mine is. It goes down when I lie down for the night and returns the next day in the afternoon.

My surgery cut many nerves, so my foot was numb on top for most of my life. Only recently it appears the nerves have regrown back, much to my detriment.