Vini Jr struck for the 1-0 Champions League playoff first-leg win, though his celebrations angered home fans. He was booked for his behaviour before he clashed with Prestianni as they walked back to the centre circle.
The Brazilian reported what was said to the referee, accusing the Argentine of alleged racial abuse. The match was then suspended for 10 minutes as per UEFA protocols before it resumed as controversy swirled.
In the aftermath, on social media, Vinicius Junior posted: "Racists are, first and foremost, cowards. They need to cover their mouths with their shirts to show how weak they are.
"But they have the protection of others who, in theory, have the obligation to punish them. Nothing that happened today has anything to do with my life or my family. I received a yellow card for celebrating a goal. I still don't understand why.
"On the other hand, it was just a poorly executed protocol that served no purpose. I don't like to show up in situations like this, especially after a big win and when the starters have to be about Real Madrid, but it's necessary."