UFC 306, the first sporting event held at Las Vegas’s Sphere, promised spectators would feel like they were part of the action. But an up-close look at a gruesome cut across Irene Aldana’s face during a preliminary bout Saturday night might have been more than most stomachs could handle.

The cut caused by an accidental head clash with Norma Dumont of Brazil was caught by cameramen and displayed across the 160,000-square-foot round LED screen. With blood streaming down her face, Ms. Aldana of Guadalajara, Mexico, fought gamely before losing a five-round decision to Ms. Dumont.

Ms. Aldana, 36, was immediately transported to a nearby hospital after the bout and received stitches from the top of her forehead down to the bridge of her nose. She also had stitches across her eyebrow and gained plenty of respect for her bravery while fighting through streams of blood covering her face.

UFC doctor Greg Hsu, who treated Ms. Aldana, posted a video of Ms. Aldana’s repaired face. “@irene.aldana such a strong & courageous human. What a superstar. Godspeed in healing!”

The two bantamweights met in a women’s non-title bout before the main card of Noche UFC 306, a celebration of Mexican Independence Day. Ms. Dumont (12-2) was by far the more accurate striker, landing 159 significant strikes to just 69 for Ms. Alana (15-8).

Ms. Aldana’s pulverized face drew gasps from the crowd mesmerized by the images and video being displayed on the massive Sphere. The $2.3 billion venue opened a year ago and hosted several concerts, but not a sporting event.

A crowd of 16,024 watched Merab Dvalishvili earn a unanimous decision over Sean O’Malley in the main event to become the new UFC men’s bantamweight champion, while Valentina Shevchenko regained the women’s flyweight title in her third fight with Alexa Grasso.

The UFC president, Dana White, said staging a UFC fight at Sphere was a “one-and-done” undertaking but a record $22 million gate, the highest-grossing UFC event in history made it a financial and visual success.

“The whole thing was seamless,” Mr. White told reporters at Las Vegas. “It went perfect. We didn’t have a lot of time to rehearse. That was our big worry coming in. But the team absolutely nailed it.”

He said the UFC won’t be returning to the Sphere anytime soon because “I’m under contract with MGM,” he said, adding the card was “meant to happen. It happened. We did it. We killed it. It translated well to television, too.”

Mr. Dvalishvili said he got caught up in the video displays on the massive Sphere. “When I was in the locker room, I saw the background change all the time and everyone goes crazy,” he said. “It was for sure different and beautiful. I couldn’t focus on my warm up and training because I was watching. But it was beautiful experience. I’m grateful. It was my dream to fight at Sphere on Mexican Independence Day and history made.”

Ms. Shevchenko said she was too focused on her fight to take in the environment but is eager to view a replay. “I can’t wait to see everything in replay because I want to see what I was a part of,” she said.

Mr. White said nearly $20 million was spent on the production. “It was all about the Sphere,” he said. “People were interested and people wanted to see it. People wanted to experience it. It was pretty cool.”