Why does my knee hurt when i bend it?

I am a male college student (19) and lift weights 4 days a week (i weigh 230) and have been doing so for 7+ years and slightly above average in body fat content regardless of my weight. Recently i’ve taken up 30 min of cardio on an ellipitical 5–6 days a week and have been doing this for 2 weeks solid now. Saturday after doing my 30min of cardio i decided to sprint a lap, walk a lap, sprint a lap, walk a lap. (on my track 7 laps = 1 mile). Now over the past couple days my left outer knee (from what i’ve found it either is or is close to the lateral collateral ligament) shoots a sharp pain when i sit down and pull my leg up (indian style ish) to put my tennis shoes on. It hurts to the point where i have changed the way i put my shoes on. Basically any side to side movement of the knee gives out some sort of pain. I was just wondering what is the problem and do you think that because being on an elliptical is a very parallel movement (without turns in it) that i could have possibly over trained a certain part of my legs and undertrained the LCL and similar tendons?