I've no idea what I've done

I pushed myself Friday to beat my personal target of 5km within 30 minutes and since my knee has hurt, could be coincidence but I can't think why else.
I only realised when I went to get in the car Saturday and my knee didn't want to follow my brain so when I was in that bend to sit in car position I hit my head off top of car

now things like the stairs I feel it achey and today running on TM I felt the pressure on it.
Not constant but randomly. Wonder what it is. #boo