Bellingham, 22, starred for Xabi Alonso’s side as they earned a 2-1 win over arch-rivals Barcelona in the first El Clasico of the 2025-26 season.
The attacking midfielder provided the assist for Kylian Mbappe’s opener and scored the winner to send Real Madrid five points clear at the top of La Liga.
Tensions boiled over after the final whistle, however, with several Real Madrid players approaching Lamine Yamal for his words ahead of the game.
Bellingham was also involved, making a lewd gesture, pointing toward his crotch while sticking out his tongue in front of supporters.
He could now face a ban having made a similar gesture at Euro 2024 after scoring for England against Slovakia, for which UEFA issued him a £25,000 fine and a suspended one-match ban.