Knee injury

Patient: I injured my knee while working out, doing jumping jacks or donkey kicks. I don´t feel any pain in the bones, it feels it´s the muscles and/or tendons. It´s not swollen nor way too painful, but it´s a nagging pain that goes down the leg. I´m taking proper rest and trying not to move it too much. My question is should I apply heat or cold?

Doctor: