It was the goalkeeper Roberto Rojas.
The incident was in a game against Brazil, during the World Cup 1990 qualifiers. Chile needed to win to qualify. After a flare was thrown into the field, near Rojas, he fell to the ground bleeding from his forehead. However, it was later revealed, through photos and videos, that the flare landed about a metre away from Rojas, who eventually confessed that he kept a razor blade in one of his gloves, and used it to cut himself in an attempt to get Brazil sanctioned, and giving Chile the win they needed.
After the scandal, Chile was banned from participating in the next qualifying process, and Rojas was banned from professional football for life.