Perez was on the receiving end of a five-second penalty for hitting McLaren's Lando Norris when he tried to overtake the Briton.
The Red Bull driver argued Norris was to blame as he felt he was ahead, while Norris said he was actually making room to let Perez pass on purpose, although the Mexican crashed into him anyway.
At the time, Perez vehemently disagreed with the penalty, which demoted him from second to fourth at the finish.
And after crossing the finish line he further lashed out at the stewards on the team radio, saying: "The stewards are a joke, man. I cannot believe it. They have been very bad this year, but this is a joke. That was really a joke."
The stewards summoned Perez for his comments and, after receiving an apology, they settled on giving him a formal warning.
In their verdict, the stewards said they have no issue with public criticism, but thought Perez crossed the line of "personal insults", which is in breach of Article 12.2.1 k) of the International Sporting Code.
"The Stewards explained to the driver that they had no issue with someone disagreeing with their decisions, however comments that amount to personal insults are a breach of the International Sporting Code," their statement read.
"The Stewards note that they are obviously conflicted in this matter as they were the subject of the radio statements and that normally this would be referred to the next panel of Stewards. However as this is the final event of the season, the matter needed to be dealt with here.
"The driver made a genuine and sincere apology to each of the Stewards and explained that he made the comments in the heat of the moment and did not consider the fact that they would be broadcast, and the impact of that.
"He expressed his regret that his comments caused offence to anyone or harm to the sport, which he said he was concerned to avoid. The Stewards accept his statements and accept his apology.
"The Stewards also note that the driver is not known for making such comments and has always been extremely respectful in Stewards hearings."
The stewards detailed that Perez still disagreed with their decision to penalise him but could now understand their perspective.
