The 22-year-old has missed Chelsea's last three games due to the problem, but could return to Jose Mourinho's side for their final Premier League match against Cardiff City.
"I'm not playing because I felt a pain due to an injury to my hip, so, in the last game against Liverpool, I was not called on," Oscar told Globo.
"I warmed up [against Atletico Madrid] but Mourinho knew that I could hardly play. Maybe I will not play the next game because I could suffer a more serious injury to my hip and he knows it.
"We're aiming to try and play me in the final clash of the Premier League but I have to take care for the World Cup."
The Blues are still in the race for the league title due to being two points behind leaders Liverpool with as many games remaining.
However, their Champions League hopes were dashed following Wednesday night's 3-1 defeat to Atletico Madrid at Stamford Bridge in the semi-final.