Thanks for posting your worry.
You are having an ankle injury
with mechanism being twisting. This could result in either just a sprain
or more complicated to dislocation or temporary dislocation of ankle joints (with immediate reduction or normalization to original position) or fracture
of either the distal tail of the fibula
or one of the complex bones of the foot ( very very rare). Also possible is rupture of tendon. The swelling is due to the twisting of muscles which resulted in inflammation. So what to do now? You should visit an orthopedic surgeon or your doctor for close physical examination and an x-ray will be done to determine the kind of lesion you are having. If you are having soft tissue
damage (inflammation or rupture) then corrective medical or surgical measures will be used. For the pain you will need analgesics ( orally or locally to massage
). If rupture surgery will need to be performed depending of the extend of the damage. To actually diagnosed the type of soft tissue damage a CT scan/MRI might be needed.
If bone lesion ( joint dislocation or fracture), reduction would be indicated and immobilization of the joint with a POP or open reduction and nailing. Which ever method it will be decided by the orthopedic surgeon.
But you should not be alarmed, it might just be nothing to worry about and with a couple of days to weeks, you will feel a lot more better.
Hope this helps