Well if you think it is just a sprain I would ice it for a while. Something to handle swelling would be good, I will not tell you what as that makes me liable. If the pain or swelling gets worse in the next 12 hours you need to have it looked at.

Just call your service provider and make sure you also have your phones IMEI number handy. If you paid and its your phone they will help you right away after verifying a few details.