Beasley needed treatment to reduce swelling above his eye following Thursday's game against Detroit, and reports initially said the reason was that he struck himself in the face out of frustration for mistakes on the court.
Beasley said Friday he did hit himself as he ran back down the court during the third quarter of the win.
But Beasley, Heat coach Erik Spoelstra and team officials said the wound above Beasley's right eye was the result of an inadvertent blow he took from Pistons forward Jonas Jerebko as he attempted to block a shot in the third quarter, not from a self-inflicted punch.
"I watched the video, and it does look like I knocked the mess out of myself," Beasley said before Friday's preseason game against the Charlotte Bobcats at the Sprint Center. "I had everybody in the world calling me and asking, 'Why you so crazy?'"
Beasley finished with nine points Thursday in his first preseason appearance since he rejoined the Heat on a nonguaranteed contract this summer.
Beasley was back in the lineup for Friday night's game, scoring 13 points in 19 minutes. Miami was without guard Dwyane Wade, who decided to sit out and rest his knees instead of playing for the second time in as many nights.
Beasley then had three disappointing seasons in Minnesota and Phoenix before he was released by the Suns in August after struggles on and off the court.
Beasley said Friday he doesn't need to cause any distractions or draw any negative attention to himself in his second opportunity in Miami.
"I'm coming into a delicate situation," Beasley said. "It's not pressure, but it is a little more to think about. I don't want to be the reason the ship falls. I'm definitely taking it more serious than my first two years."