Dear friend, welcome to HCM.
you seem to be having a knee ligament or meniscal (buffer ring) injury
does your knee click on bending/ straightening?
I think you should see your ortho doc and get evaluated.
do not put stress
on the afftected leg. take simple painkillers (like t. paracetamol
3 times a day till the )
hope to have satisfied you. get well and keep posted.