It can take up to 6 weeks for a sprained ankle to fully heal, as long as it takes for a fracture.
Do not drive a car whilst you have a sprained ankle as you will not have any insurance.
If there is pain on palpation in the malleolar region and one of the following:
i) over the bottom 6 cms of the posterior edge of the Tibia or the medial malleolus (the bony protuberance on the inside of the ankle)
or
ii)over the bottom 6 cms of the posterior edge of the fibula or the lateral malleolus(the bony protuberance on the outside of the ankle)
or
iii) Unable to weight bear immediately and for four steps some time later., e.g. in the Emergency Department
then the ankle should be x-rayed to rule out a fracture.