The United winger was cautioned by referee Chris Foy in the second half of Sunday's game at Wembley following a challenge by Ledley King inside the box.
Foy cautioned the Portuguese ace for simulation, but Ronaldo is adamant he was caught by King and was unfairly treated by the match official.
"If you see the replay you will see that their player kicked me in the foot," said Ronaldo.
"The referee did not make the right decision then and he didn't give me a lot, all match, I don't know why.
"But in every game, the referee's decision has to be respected."
Feet on the groundRonaldo, who hit the post at the end of normal time, stepped up to score in the penalty shoot-out and was happy to find the net after missing against Chelsea in last season's UEFA Champions League final.
He added: "It's always important to choose a side and put the ball there.
"After Moscow I thought the goalkeeper would think I put it in the same corner but I changed."
United's Carling Cup success has only fuelled talk of a famous quintuple this season, but Ronaldo is not getting carried away by the chance to make history.
"It is quite hard," he said.
"We have to think game to game. We won this cup now, we are top of the league and still in the Champions League and FA Cup.
"With United there is always an opportunity to win everything but we need to keep our feet on the ground."