There were fears the influential Ivory Coast international could miss the remainder of the season after limping out of Sunday's defeat at Liverpool with a leg injury.
Pellegrini has now said the problem is not as bad as first thought but Toure could still miss key Barclays Premier League games against Sunderland, West Brom and Crystal Palace.
Pellegrini said: "Yaya has a muscle injury. We will see with the doctor how many days.
"Maybe it is not so hard as we thought at the beginning but I think he needs at least 10 days or two weeks to recover."
City will hope Toure will be fit to return for City's vital trip to Everton on May 3.
The loss at Anfield left third-placed City trailing leaders Liverpool by seven points, although they still have two games in hand.
They play the first of those extra fixtures on Wednesday as Sunderland visit the Etihad Stadium in a rearranged game.
Captain Vincent Kompany, who suffered an injury scare prior to what proved a chastening afternoon, and top scorer Sergio Aguero have both been declared fit.
Aguero played 22 minutes off the bench on his comeback after a five-game absence with a hamstring injury.
Pellegrini said: "Vincent is okay. He is fit, he is in the squad list.
"Sergio is in the squad list also. We will see tomorrow (who) the 11 starters (are)."