1. Did u develop swelling in your knee? if yes - within an hour or gradually?
2. If you developed swelling then u need to consult nearby orthopaedic doctor to rule-out any bony or ligament / meniscal injury
3. if you didnt develop any swelling then its mostly a non-serious thing : Use crepe bandage, give rest to the knee for a week or 10 days by using knee brace
or knee cap.
4. Persistent pain warrants examination & consultation by orthopaedic doctor.