Heard a 'crunching' sound in left knee when attempting to lift hips off heels

Hi there,

I went into toe stand on my left leg. My balance was good enough on this day to put both hands in namaskar and look in the front mirror so the teacher prompts me to ‘give it a go’ lift my hips off my heels. So i did. I stupidly just went for it and as my hips come off my heel i heard a crunching noise then felt pain and fell out of the pose. It swelled quite quickly, a bit of bruising the next day, very sore to touch at the top of the knee cap and i can hardly bend it. Do you think maybe its a tear, a strain?

At me next class i could hardly do any of the postures as i felt the pain in my knee. Its very frustrating.

Thanks in advance.