Madrid left Camp Nou with a 2-2 draw in a thrilling encounter, fighting back from a goal down on two occasions.
Luis Suarez gave Barca an early lead before Cristiano Ronaldo – who was withdrawn with a knock at half-time – equalised soon after.
Despite having Sergi Roberto dismissed just before the break for appearing to strike Marcelo in the face, Barca restored their lead early in the second half through Lionel Messi, only for Gareth Bale to secure a point.
Real Madrid appeared to be denied a chance to take the lead when referee Alejandro Hernandez failed to whistle a foul despite Marcelo going down in the area after apparent contact by Jordi Alba.
Madrid also claimed Messi's goal should have been waived off due to a foul by Suarez on Raphael Varane.
And Ramos says Messi put Hernandez under pressure in the tunnel at half-time.
"Messi has put a little pressure in the tunnel," he is quoted as saying by Marca.
"I do not know if there were cameras, I don't know if in the second half he will have done it in other ways.
"It's football and everything has to be left on the field, as long as it's not going to hurt you. You have to have that respect."
Ramos' team-mate Casemiro also noted the potential penalty, but had sympathy for the referee in a match that he considered a fair result.
"The referee could have given a penalty for Marcelo," Casemiro added. "But we cannot talk about him, the referee wants to do his best. It was a draw, a great match for both sides.
Suarez, meanwhile, admitted he did not expect play to continue after his challenge on Varane.
"Varane controlled it and I just put my foot in," Suarez said. "But hey, that's the decision of the referee, sometimes they get it right and sometimes not, I was a little surprised that he let it go on.
"We went ahead twice on the scoreboard. Sergi's red card hurt us, but the team did spectacular physical work, defended well. The draw was not bad either."