Donald Cerrone vs. Tony Ferguson was the unofficial people’s main event at Saturday’s UFC 238, with MMA fans ecstatic to see “Cowboy,” the win leader in the UFC with 23, and Ferguson, who was on an 11-fight winning streak heading into the bout, go at it. And they delivered.

The two lightweights threw down for two rounds before the doctor stopped the fight due to the severity of Cerrone’s injuries and awarded Ferguson the win by TKO. His nose was puffy and red—a sign of it being broken—and his right eye was swollen completely shut.

At first, some fans thought that it was the shot that Ferguson landed after the bell that put “Cowboy” over the edge, but that was later cleared up. “The punch had nothing to do with it,” Cerrone said in his post-fight interview. “I don’t quit, I don’t back down and, man, I just wanted to keep fighting.”

In the same interview, UFC commentator Joe Rogan said, “You blew your nose, which is something you’re never supposed to do, and your eye swelled up.” Apparently, when a fighter’s nose is broken or badly injured, they’re advised not to blow it. Check out this video of MMA veteran Eddie Alvarez giving his nose a honk and then his eye immediately swelling. 

Rogan may be in on this gross trade secret, but we’re guessing that a lot of you MMA fans have (probably) never heard of this before. To get some more info, we spoke to the lead cutman of Bellator MMA, Matt Marsden.

“It’s like when you try to clear your ears after a flight—that’s called a Valsalva maneuver,” Marsden said. “When a fighter has a broken nose and attempts to blow their nose, they’re doing the same thing. It increases the blood pressure, causing the already bleeding and torn blood vessels in the area to open, and all that air and blood has nowhere to go except behind and around the eyes, and that’s what happened to ‘Cowboy’ Cerrone.”

While Cerrone was landing shots in the first round, Ferguson’s pace wore him down in the second and he was susceptible to shots. He was already battered, but blowing his nose was the final straw. “When a fighter’s vision is blocked, the fight needs to be stopped, Marsden says. “There could have been any number of underlying things happening under that swelling, most commonly orbital fractures, that have weakened the overall structure of the eye. One more hard shot and that could end a fighter’s career and leave them blind.” 

While fans hated to see the fight stopped, we’re glad “Cowboy” is on the mend. Now, with his title run stopped short, we’re wondering who he’ll take on next. Once that eye heals up, of course.