However, the 22-year-old is confident of returning to action before the end of the La Liga season.
"I knew it could be a long time out and I was a little scared. I don't like it in any way and then there's the World Cup, of course," Neymar told Globo.
"But I can return within three weeks and hope I can play in Barcelona's last match.
"There'd been swelling that had bothered me for some time. The most I could do was get to that game. I was bothered a lot and had difficulty walking after."
Neymar has scored 15 times in 40 games this season.