The Brazilian put past his own keeper to cancel out Javier Pastore's opener, which les Parisiens' coach says was unfortunate, while Ranieri was satisfied with his side
Javier Pastore had given the visitors the perfect start at Stade Louis II with his first Ligue 1 goal of the season as the Argentine met a deflected header from Alex to head past Danijel Subasic from close range.
Zlatan Ibrahimovic had three good chances saved by the Monaco goalkeeper, but the champions still looked on course to secure victory until Thiago Silva's 74th-minute own goal.
"The first half was better controlled, but after it was a bit more complicated," said Blanc.
"We came to win, and dominated the first half. We thought we could win. The [own] goal is a bit unfortunate."
The result sees PSG remain five points clear at the top of the table.
Meanwhile, Monaco coach Claudio Ranieri declared himself content with his side's display.
"I am satisfied; we had a good game against PSG," said Ranieri.
"At half-time, I made changes to the system. I positioned three central midfielders and decided to play a diamond, both to attack, but also to release [Layvin] Kurzawa [on the] left and Fabinho on the right."
Ranieri insists claiming automatic qualification for the Champions League by finishing second remains his main goal.
"PSG is a great team. We are building," he added. "We have many good players but this is the first year they evolve in Ligue 1.
"The experience is very important. We are ambitious, but we played against a great team that plays in the Champions League.
"We must continue playing for second place; our goal is the Champions League. If PSG wants to lose the title, we're here."