I teisted my knee 25 years ago playing squash. I have twisted my ankle harder than I twisted my knee that day.
It swelled up to the size of a grapefruit. Turns out I had torn my ACL.
Had surgery about a year later and other than some bone damage I did to it twiating a 2nd time before I had my surgery it's fine.
Get it looked at by an ortho asap.