Any insight into why my leg in swollen after jumping rope?

So with winter upon me I've taken up jumping rope for my cardio workout. Well yesterday I did it for 30 minutes. Totally kicked my butt and felt GREAT afterwards. However, I noticed my left leg was swollen from the knee down. No pain and nothing "tweaked" during the workout. But after I pulled my sock off you could see the swelling. Any ideas? Should I be worried? It doesn't hurt so it's not limiting me from doing my workouts but swelling isn't normal ya know.

Thanks people.

Maybe you hyper extended your knee, go to a ortho and see