Knocked 2nd Woman Down Before Stabbing

4:32 PM PT -- Terrelle Pryor knocked a SECOND woman to the ground before getting into a physical altercation with Briston, a witness told police.

TMZ Sports obtained the court docs with witness accounts of the incident and it's insane -- essentially saying Pryor and Briston got into a huge fight earlier that night that turned explosive.

A witness told cops ... Pryor, Briston and friends had gone out to dinner and drinks when the couple -- who have been dating for about a year -- began arguing.

Briston and her friends went to the club and Pryor went home -- but when the group got back to Pryor's place after partying, he was waiting in the hallway pissed off.

One female witness -- a friend of…