I've never heard of marijuana causing bleeding issues but I certainly wouldn't go to court and swear on the bible. It seems pretty unlikely that the ganja would have caused your bleeding problem EXCEPT....were you blazed when you went head over heals?? Then AHA!!! (just kidding)
I'd definitely call your doc in the morning and let him know you've had nosebleeds....that plus perhaps a head injury.....see where I'm going here.....???

That yellow stuff in your knee is probably serum......blood seperates into two parts as you know....the red cells etc.....and the serum.