It might be due to Patello femoral pain syndrome, in which there is pain is infront of knee or arround knee cap.
~Vigorous Activities like stair climbing,kneel down ,squatting,jogging is the cause.
~Problem in alignment of hip,knee and ankle,muscular imbalance may also aggravate your pain
Next Steps
stop doing activities which is causing pain untill it is resolved .
Health Tips
~low impact activities should be done.
~if you are overweight losing weight will help to reduce pressure on knee.
~shoe insert can help to align if hip-knee-ankle aligmnent if it is not proper.
~quadriceps strengthening exercise ,stretching of tight muscle especially hamstrings and calf will help.
~for further guidance visit physio.