Hurt knee (fell hard) on Sat couldn't walk on it still pain no bruising. Can walk now but streaky black bruising and redness on knee any ideas?

Takes time . You probably sprained your muscle. Typically skin and muscle inflammation takes few days to weeks to completely heal. Take anti inflammatory medicines. Elevate the swollen part over the pillow. Avoid exertion but use the affected part. Eat proteins diet. If no open wound and swelling and pain is better that is good. If pain and swelling become worse, or redness increases or open wound see Dr.