Rolling your ankle after a awkward landing or tripping over a curb is a common cause of a sprained ankle.

Initially it may be too painful to stand or walk but sometimes that improves within a few hours or by the next day.

If pain lasts more than a day or two, it is possible you may have a sprained ankle.  The sprain is actually damage to the ligaments that support and stabilize the bones in the foot and ankle. 

A minor sprain (a partial tear of one or more ligaments) may be treated with a brace or boot and typically improves within a few weeks.  Limiting activity may prevent further injury.  Ice, medication, and compression may be all that is required. 

A more significant injury may mean one or more ligaments has been fully torn so it is not attached to the bone anymore. This requires longer to heal and may mean more time in the brace or boot. 

Sometimes surgery to reattach the ligament is the best option.   Surgery involves reattaching the ligament to its original attachment site to stabilize the ankle.  A boot or cast may be required after surgery to protect the repair until it fully heals.