The 24-year-old, whose leg became infected following an injury, has made 12 appearances for the club this season.
"A simple knock on it and he could have been out for the rest of the season. It is important that our concern is chiefly with the player's well-being," Pearson told the club's official website.
"He needs to get it sorted, but he is well on the way to recovering now. Hopefully it won't be too many weeks, but it will be a month or so."
De Laet joined Leicester from Manchester United in 2012.