Hi, thanks for writing to HCM.
Based on the description and symptoms , I suspect that you could have suffered a soft tissue injury
in the knee joint either of the meniscus
or the patellar fat pad.
A detailed clinical examination and possibly MRI scan may be needed to diagnose your problem correctly.
In the meantime, avoid making any movement that produces the pain. Use ice packing over the painful area once in 2-3 hours to alleviate the pain & inflammation. Take simple analgesics like Diclofenac
as and when needed.
If your symptoms are not improving within a few days, consult an orthopedic surgeon for further evaluation and management.
Hope this information is helpful. Good day