Madrid was dominating the match at Camp Nou and Barcelona right back Sergi Roberto was shown a direct red card in first-half injury time for swiping his hand at Marcelo's face as tempers flared between the rivals.
The home fans were raging as the half-time whistle blew but, with Marco Asensio on for Ronaldo, they were celebrating eight minutes after the restart.
"He doesn't feel good now, but I don't think it is anything serious", Zidane said.
"We watched an incredible game of football and I can't say if the draw is fair or not", said Real coach Zinedine Zidane, who would not be drawn on the referee's performance.
Bale had risked getting sent off for raking his studs against Samuel Umtiti's leg but escaped without a booking on that occasion and Roberto was sent off moments later for hitting Marcelo following an off-the-ball tussle.
Real dominated the later stages of the game as they sought to end their opponents' proud record this season, but the hosts held firm.
There was nothing too much to play for but pride and honour in the eye-catching encounter as the Catalan giants have already been crowned league champions.
Ronaldo's ankle appeared to be trod on by Barcelona defender Gerard Pique as he scored Madrid's first equaliser in the 15th minute.
Real Madrid soon took control of the game with Kroos who would then combined excellently to set up Ronaldo who levelled for Madrid. We have a match and we want to win.
"We will see how we are going to play", he continued.
Messi looked poised to get another goal but Bale made it 2-2 by using one touch to curl Asensio's pass around Ter Stegen. Real did not put the ball out of play at the time, angering Barca players.
The tension began to rise as Alba and Modric squared up, so did Suárez and Sergio Ramos, before Messi was booked for a foul on the Madrid captain. We have many players to come in for those missing, and that is the most important thing.