Whenever you have a chance to take a break, take off your high-heels and soothe your feet with some ice packs. If you have an employee fridge in your break room, keep one of those bead-filled bags (the ones you can pop in the freezer or microwave for pain relief) in the freezer and use it whenever you have a few minutes off your feet. Repeat the ritual when you are at home.
Take pain relievers and anti-inflammatory medicine - you might even want to start your work day with a dose in your system to prevent the pain from getting out of control, as much as using it to stop the pain once you already have it.
Spend a few minutes again with your ice packs at the end of the work day, before you go home, and then switch to shoes with very good support as soon as you are ready to leave work.
I have a peppermint foot balm that is a favorite for rubbing on sore tired feet at the end of my shift - I think the combination of the peppermint scent, the cooling effect of the peppermint oil in the lotion and the massage gives a lot of relief too.