Hyperextended knee

27 YOF no pertinent medical hx, no meds besides ibuprofen and Tylenol, no allergies.

I hyperextended my left knee backwards after being tackled during a game. It went back far enough that it was obvious to onlookers and was immediately painful. I'm wondering how seriously I should take it

This happened over 48 hours ago, and it hasn't improved as much as I was hoping with rest and ice. I've also taken ibuprofen and Tylenol for the pain.

When it first happened, I had to keep working for 6 hours mostly walking and carrying things. I had a pretty bad limp and couldn't straighten my knee or bend it past a certain point. Stepping wrong would cause my leg to buckle and sharp pain.

Currently, when straightened I feel something pulling uncomfortabley at the back of my left knee, but no real pain. When I bend it without weight on it, it pulls at the front of the knee- again uncomfortable but not really painful.

I cannot really bend it AND put weight on it. Going up and down stairs it buckles and sends sharp pain shooting up my leg. I cannot run. The only improvement is that I can walk without a limp if I move slowly and deliberately, which was not the case for the first 24 hours.

Finally, the more I use it to walk over the course of the day the worse it gets. By the end of the day, there is a horrible clicking that isn't exactly painful but is like nails on a chalkboard to me.

I'm supposed to do PT tomorrow, and I'm not sure I'll be able to perform. How serious is this, will it just go away with rest?