Per NFL Network's Ian Rapoport, Lynch was fined over $24,000 for unsportsmanlike conduct involving a referee.
Raiders quarterback Derek Carr fumbled the ball out of the end zone on the team's final offensive play in a 20-17 loss against the Cowboys.
After the officials reviewed and confirmed the ruling on the field of a turnover, Lynch was flagged for unsportsmanlike conduct while arguing with the referee about the call.
Following a one-year retirement in 2016, Lynch has had a successful comeback with the Raiders this season. He leads the team with 163 carries, 695 yards and seven touchdowns.
The Raiders are 6-8 this season, two games behind the Kansas City Chiefs in the AFC West with two games remaining.