With given details, it's highly likely to be fibular joint dysfunction. In some cases, rotation of fibular head due to severe strain can also cause lateral knee pain and swelling. If symptoms persists, consult a physiotherapist who can assess the cause and he/she may recommend procedures like manual mobilisation of fibular joint and taping if necessary.
Next Steps
ice packs (10-15 mins. application) can help in bringing down the pain and swelling.
Health Tips
Avoid squats, jogging and walking on uneven terrain.