Vinicius scored both goals for the Madrid Castilla in their 2-2 draw with Atletico's B team in Majadahonda.
The major talking point of the match came when Atleti captain Tachi tangled with Vinicius and both fell to the ground, at which point it looked like he attempted to bite his opponent on top of his head.
Both players were booked by the referee, but no further action was taken.
Tachi concedes he set a bad example for the rest of Atletico's youngsters but says he and Vinicius made peace after the match.
"It's a reaction that came under the high pressure of the match," he told the club's website. "I'm not proud of what happened and it does not reflect anything about me as a player.
"This action is not representative of anything instilled in us by the academy and I know it is not an example for people watching at home to follow. It does not represent the way I play and it is a pity that this action has taken prominence and eclipsed a good game from us against Castilla.
"At the end of the game, I spoke to Vinicius. We gave each other a hug and everything was left there. Now I have to learn from this and move on."