Griffin wrote "Heart" on the left side of his undershirt worn on the field prior to the Redskins-Saints game on Sunday. Whether or not the personalized message was intended to inspire his game or help one of his marketing partners is up for debate.
Players are not allowed to cover up Nike's swoosh, but can wear other brands if they are official NFL licensed providers.
Griffin, like most highly drafted NFL rookies, has been educated on the league's brand protocols.
NFL spokesman Brian McCarthy told ESPN.com that league officials would talk to Griffin. "It won't happen again," McCarthy said.