The Portugal captain was left limping in the final minutes of Wednesday's Group B clash in Sofia with an apparent ankle injury following a late challenge by Anicet Abel.
Ronaldo had earlier cancelled out Marcelinho's sixth-minute opener with the second of two spot-kicks, the first of which was saved by Ludogorets goalkeeper Vladislav Stoyanov, before Karim Benzema netted the winner.
"It was an intentional kick and we’ll see [on Thursday] how it is, but it's a little open at the moment,” he is quoted as saying.
"It was a very ugly tackle and it seemed as if we were playing a game of rugby, but the most important thing is we got the three points and are now half-way towards qualifying for the next stage."
Speaking after the match, coach Carlo Ancelotti said of the complaint: "Cristiano has had a knock. It's painful but nothing serious."
