Yeah, you better had. I had a bad breakfall three years ago with sumi-otoshi. Must have landed with my ankle hitting the floor first as I had a huge pain about an inch below my knee that went in a straight line across my leg - thought I'd broken it for an instance.
Anyway, the back of my knee became swollen to about the size of an orange. I don't like bothering the doctors so I thought I'd give it a day or two and see how I get along. Swelling went and pain subsided so practiced Aikido with a knee support for a while.
Reason I'm telling you this is that this was three-years ago and for some reason it's started hurting again. So, get to the docs and sort it out