How can I relieve an injured foot, swelling and lots of pain?

Depends on injury. If you are sure you are not seriously injured, rest ice and elevate are the best way to reduce swelling and pain. Ibuprofen or Aleve (naproxen) if you can take them.
Get an x-ray. You will need and x-ray to see if you have a fracture or if it is just a soft tissue injury. If fractured, you will need to be immobilized with a splint, cast, or rigid walking boot depending on the location of the injury. If fractured, it may need to be reduced in the office or possibly in the operating room. Have it evaluated by your physician to get the appropriate treatment.

Related Questions

2 wks ago I injured my shin, then swelling moved to my foot. Swelling has gone down, but now I have pain in areas of foot where swelling remains.

Slow process. I assume bruising and discoloration occurred & moved along with the swelling. This is blood in the tissues outside of the vessels which causes swelling and pain. Until all the old blood released by the injury has been absorbed by the body processes, there will still be some swelling and pain. Warm/hot soaks followed by cold water/compresses activate the circulation and speed it up. 2+ times/day. Read more...