What to do if i sprained my foot and when i try and walk my foot turns purple?

Can be normal: As long as you have been examined and had xrays, then swelling and bruising after a sprain is normal. The worst swelling is usually 4-5 days after the injury.

Have it evaluated.: Swelling and bruising may last a long time following a foot or ankle injury. An x-ray can show if there is an underlying fracture. You may have a soft tissue injury if it is just a sprain and may have damaged the muscle, tendon, or ligaments in the area. Have it evaluated by a professional and get the appropriate treatment.