I was sitting on this char yesterday so I went to the kitchen and it started to hurt me. The pain vanished later but it came back like 2 hours ago and it hurts even more.
Is the pain coming from the outside of your leg? From your description I'd say its a knee problem man. There's a band of tissue that stretches from the points you mentioned on the outside of the knee. Sounds like you've somehow stressed it. I did the same once, its not too bad if you just rest it properly and treat it with anti-inflammitories.