The Rossoneri remain top of the table, but Nesta says it was a setback.
"We have lost two important points," Nesta told the club's official website.
"Even if we didn't play very well, above all in the first half, we were bringing the game home.
"It's a shame. We made hard work of keeping the ball and were a little naïve on the corner, which resulted in their goal.
"We are bitter. We have to accelerate our season.
"There is a big regret, but we are going forward regardless."