McMillian did not lead with his helmet but appeared to use his shoulder to hit Scheffler in the head during the fourth quarter of Sunday's game at Lambeau Field.
The league said McMillian was fined for "striking a defenseless receiver in the head area with his shoulder."
Scheffler has not practiced all week because of a concussion.
It's the second time McMillian has been fined in as many seasons. He was fined $21,000 last season as a rookie for a hit against New York Giants tight end Martellus Bennett.
ESPN.com Lions reporter Michael Rothstein reported that Detroit defensive tackle Ndamukong Suh was not fined for tripping Packers quarterback Aaron Rodgers in the first quarter of Sunday's game. Suh was penalized on the play.