The 22-year-old was carried off on a stretcher in the final moments of the routine victory, but was quick to reassure fans that it was not a serious problem.
"It was an isolated incident, I felt a pull in my leg," he told the club's official website.
"The doctor told me it would be best to go to the changing room. I hope it's nothing and I have a good feeling about it.
"I want anyone who is worried to relax, in two or three days I'll be fine."
Left-back Marcelo scored the second of Madrid's goals to send Carlo Ancelotti's side three points clear at the top of La Liga after Barcelona's 1-0 defeat at Real Valladolid on Saturday.
But the Brazilian knows their great rivals will respond strongly as the title race looks set to go down to the wire.
"We couldn't slip up today, so we focused more on the job at hand," he said.
"We can't count out Barcelona as they're a top side and we respect our rivals always.
"Now we have a week to rest a little bit and to continue trying to win every game."
