Carvajal delayed a throw-in during stoppage time at the end of Madrid's 6-0 demolition, with referee Artur Dias Soares showing the full-back the only yellow card of the game.
The UEFA Control, Ethics and Disciplinary Body now plans to investigate the incident to examine whether Carvajal was guilty of breaching Article 15 of its Disciplinary Regulations by "receiving a yellow card on purpose".
Carvajal's booking, his third of this season's Champions League, means he would be ruled out of Madrid's matchday six clash with Borussia Dortmund through suspension, freeing him to return for the knockout rounds.
But should UEFA opt to punish the 25-year-old over the incident, Carvajal could be handed a two-game ban, with Madrid already having guaranteed their qualification from Group H.
In the 2010-11 Champions League, then-Madrid coach Jose Mourinho and the club's players Sergio Ramos and Xabi Alonso were charged over alleged deliberate yellow cards.