Think I've done something!!

Howdy. Well I went out today for my first run since I graduated. By heck it felt good. One problem though. After my run I felt tight in my left leg. I did my usual walk around but it felt awkward so I went over to a near by fence that was quite high. Put my foot up top and leaned into a stretch. Soon as o cot home I felt what I can only describe as a pinched nerve in the knee. As the day has gone on ive now got pain just above the knee a little to the left and also behind the knee. I went shopping and got out of the car and had a terrible pain in the calf so I did a gentle leg stretch pulling my foot towards me bum and the pain In the calf went. Urgh bloody hell, do you think I over stretched my leg after my run ??