City fell seven points behind Liverpool after a 3-2 defeat at Anfield, although they still have two games in hand, with Toure limping out of the action with only 19 minutes on the clock.
The Reds roared into a 2-0 lead thanks to goals from Raheem Sterling and Martin Skrtel, before City hit back after the break and levelled through David Silva and Glen Johnson's own goal.
Vincent Kompany's late error allowed Philippe Coutinho to curl home a dramatic winner to keep Liverpool in the box seat for title glory.
Pellegrini, who is waiting to discover the full extent of Toure's problem, admitted the Reds will deserve to be champions if they extend their 10-game winning streak to 14 in the coming weeks.
The Chilean told Sky Sports: "It's difficult for Yaya to be in the next game. We will see tomorrow, I don't know how serious he is injured.
"I think it will be difficult for him to finish playing this season.
"We will continue fighting, nothing is finished today.
"If Liverpool win their four games that they have to play and win 14 games in a row they deserve to be the champions. If they don't win their four games, we are going to be.
"The title didn't finish today."
Pellegrini felt his side were very unfortunate to leave Anfield empty-handed and believes they were made to pay for not converting more of the chances they created.
He added: "It was a disappointing day because we lost a game that we didn't deserve to lose. We played very well, particularly in the second half and the last 15 minutes of the first half.
"We had clear chances to score, but football is made from good things and mistakes, and we made a mistake and they won the game.
"Liverpool started very well, so it's easier when you're playing at home and are two goals in front. But after that we rearranged things and we finished the first half with two clear chances.
"In the second half, I think there was just one team on the pitch, we scored two goals and had two or three clear chances to score. There was also a clear penalty when Skrtel handled - it was very clear.
"We made that mistake on the third goal and they finished up winning the game."