Williams was able to get up and run off the field under his own power and returned to the game later in the drive.
Jon Kitna threw a deep ball to Williams, whose back was turned to Collins when the safety came in and made contact with the back of Williams' head with his helmet. Collins was flagged for unnecessary roughness.
Williams crumpled to the ground face first near the Packers' sideline while quarterback Aaron Rodgers and other Packers players hurriedly called for the Cowboys trainers.
After Williams' helmet was removed, he got up and jogged off the field without assistance.
The league is closely monitoring helmet-to-helmet hits, saying they can result in suspension. Williams said he was fine after the helmet-to-helmet hit, then appealed to NFL commissioner Roger Goodell not to fine Collins for the hit.
"Commissioner Goodell, don't fine the guy," Williams said. "It wasn't that bad of a deal, he shouldn't get fined. It was a football play, a football player making a football play. No injury, no harm."
Meanwhile, Cowboys starting defensive end Marcus Spears did not return to the game after suffering a left calf injury.
Stephen Bowen replaced Spears on the first team.