Ronaldo went down in the box in the opening moments and the referee pointed to the spot, but Ronaldo joined Persepolis players in disputing the penalty. Referee Ma Ning checked the pitchside monitor and overturned his decision.
Al-Nassr defender Ali Lajimi was sent off in the half for a dangerous challenge on Milad Sarlak, and Ronaldo gave his Saudi Arabia team a late scare when he exited with a neck injury.
The draw sees Al Nassr qualify for the knockout stages as the Group E winner with one match left to play. The Riyadh team came into the game having won 18 of its previous 19 games in all competitions.
In the same group, Qatar's Al-Duhail earned its first win after defeating Istiklol of Tajikistan 2-0. Prolific Kenyan striker Michael Olunga scored both goals.
Earlier in Group C, Argentine coach Marcelo Gallardo picked up his first win since being appointed by Al-Ittihad this month after the Saudi Arabian champion defeated AGMK of Uzbekistan 2-1 to move into the knockout stages.
Late in the game in Tashkent, Martin Boakye pulled a goal back for AGMK.
"We had to work hard from the first whistle but we kept trying to get forward as much as we could and Hamdallah came good with two well-taken goals," Gallardo said.
The top team from each of the 10 groups of four in the tournament, which is divided into two geographic halves until the final, advances to the round of 16 along with the six best-placed runners-up.