Pellegrini's men returned to the top of the table on goal difference following a breathless triumph at Goodison Park - a ground where they had tasted defeat on their previous four visits.
Liverpool and Chelsea can leapfrog City by winning forthcoming games against Crystal Palace and Norwich City respectively.
However, victory over Aston Villa on Wednesday, in City's game in hand, will almost certainly leave the destiny of the title in the hands of the 2011-12 champions ahead of West Ham's visit to the Etihad Stadium on the final day.
Pellegrini is still taking nothing for granted as a battle for supremacy featuring numerous twists and turns snakes towards its conclusion.
"Three points is a huge step for us to continue trying to win the title," said the former Villarreal and Real Madrid boss.
"But I think we haven't finished yet - that for me is more important.
"It was one of the three games that we must win if we want to win the title.
"It was a very difficult game because you see the history here in this stadium from Manchester City - I think we won just twice in the last 10 (15) years.
"I think that Everton is in a very good moment. They play very well so it makes it a very important win."
Ross Barkley brought Goodison Park to its feet with a sensational opening goal but Sergio Aguero restored parity and Edin Dzeko netted either side of half-time for the visitors.
City inexplicably let the game drift and their two-goal cushion was halved by Romelu Lukaku's 65th-minute header before Everton pushed in vain for an equaliser.
The scenes at the final whistle were in stark contrast to those when City lost seemingly decisive ground in a 3-2 reverse at Anfield three weeks ago, but Pellegrini's mantra remained the same.
"Talking to the players and in the press conferences, especially after we lost against Liverpool, I said that that title was not over and that we must continue playing," he added.
"We tried to do our best in this moment, depending on when we can do in the future.
"That is why it is important not to have an excess of trust and try to win the next game."
‘Maybe I’ll be signed by Wrexham, who knows? English football would suit me – if an offer came, I wouldn’t think twice, I’d go immediately’ Euro 2024 cult hero reveals his UK dream
‘Managing Leeds? It was an option that appeared, but it wasn’t the right timing. I decided it wasn’t a good idea to leave the club I was at mid-season’: Premier League boss admits to turning down opportunity to replace Jesse Marsch in 2023
