Lawson, defensive tackle Jordan Phillips and other Bills players walked from the sideline toward the front row of stands at Lincoln Financial Field and started jawing at Eagles fans. Phillips got close to one fan's face before Lawson walked up and seemingly made physical contact with the spectator, according to video circulating on social media.
Security eventually intervened and the fan continued to shout toward the Buffalo players. Defensive end Leonard Floyd tried to defuse the situation and walked the players back to the sideline.
Phillips addressed the matter on Instagram, posting Monday: "I love the crowd I love rowdy fans it makes the game fun. But one thing I'm not going to tolerate is someone threatening me or my family. This is a line that shouldn't be crossed."
The Bills did not immediately respond to an email from The Associated Press seeking comment Sunday night.
The Eagles beat the Bills 37-34 in overtime.
The Associated Press contributed to this report.