Universitario's Carlos Olascuaga was brought down in the box in the 59th minute of Sunday's match but before the referee could blow his whistle for a penalty, Comercio defender Renzo Reanos blasted the ball into his own net in anger.
"I feel really bad, it's my fault we lost today. I want to ask my team mates and all Union Comercio people to forgive me," a contrite Reanos said on his Twitter account (@reanosrm).
Flores took a back pass and played the ball to one side of his box before missing it completely as he went to kick it to a defender. Avila nipped in to rob him and run it into the unguarded net.
Real Garcilaso are top of the standings with 54 points from 29 matches with Universitario in second place on 49 with a game in hand and Cristal third with 46 points after losing 2-1 at bottom team Jose Galvez.
Elsewhere, Universitario and Melgar have been order to play the remaining eight minutes behind closed doors of their match in Arequipa in July that was abandoned with the score 2-2.
Melgar's coach, former Peru striker Franco Navarro, was handed a 10-match suspension, reduced to eight on appeal, after grabbing the referee by the throat for denying his team a third goal because of an offside decision in the 82nd minute.
The referee, who backed his linesman over the decision which video replays showed to have been mistaken, abandoned the match.