Nosebleeds are a common trope in shonen, and it often comes with an ecchi connotation. However, there were no feelings of that sort when Gojo suffered a nosebleed in his fight against Sukuna. Instead, it was a matter of huge distress to the fans reading the manga. This feeling was aptly portrayed by Yuta Okkotsu alone.
The first time Gojo suffered a nosebleed was in chapter 228, and the chapter itself ended on this cliffhanger moment.
Naturally, the next couple of days were rife with the Gojover theories. Since the nosebleed came after the turn of Mahoraga’s wheel, many assumed that the shikigami was the reason behind it.
However, there were some wise old sages who gestured that Gojo’s nosebleed had something to do with him abusing the Reverse Cursed Technique and overusing his six eyes technique.
But then, if a general consensus were drawn back at that time, then Gojover would have triumphed.
Fortunately, Gojo survived that scare, and his nosebleed seemed like a small blip come chapter 229, because he nonchalantly wipes the blood away and continues to fight without giving up ground.
But then, Yuta, and ofcourse anxiety-addled spirits like me, knew that the nosebleed was just a Chekhov’s Gun that was hanging on the wall, waiting to be used by Akutami at the right moment.
And boy oh boy. The nosebleed did come back to haunt Gojo at the worst possible moments. Don’t worry though, the Gojover theories aren’t making their rounds this time.
But then, we did get a proper explanation for why Gojo had a nosebleed. And the wise old sages of the fandom were right. No surprises there!
Why did Gojo get a nosebleed?
The answer to this question is finally revealed in JJK chapter 230. Gojo got a nosebleed because he pushed himself to the limit by using RCT to replenish his cursed technique, which subsequently damaged his brain.

We know that every action has a reaction in the Jujutsu Kaisen universe. This idea was perfectly encapsulated in the incident where Itadori was not able to switch back with Sukuna at the detention center.
Read More: Why Couldn’t Itadori Switch Back With Sukuna At The Juvenile Center?
According to Sukuna, the cursed technique of a sorcerer is engraved somewhere around the prefrontal cortex on the right side of the brain. When Gojo and Sukuna were forcefully replenishing their cursed techniques using RCT, they were first destroying that part of the brain by using cursed energy and then healing it again using Reversed Cursed Technique.
This in itself is an extremely difficult maneuver.
Healing the brain is not as easy or straightforward as healing other body parts, especially the part of the brain which is engraved with the cursed technique. As Kusakabe points out, the brain is like black box when it comes to cursed techniques. Its inner workings are not known to anyone.
So taking a gamble and repairing this part of the brain with RCT is more dangerous than playing the Russian Roulette. It’s a fatal gamble and somehow Gojo managed to survive it four times.
However, the constant process of destroying and healing took its toll on the brain. It’s bordering on abuse.
And because of this Gojo was no longer able to use his domain expansion, which is basically the process of realizing and bringing forth your innate domain.
It’s good to know that Akutami is putting in repercussions for the out of the box ideas that these two mentality beasts are coming up, making the fight all the more realistic and enjoyable.
Well, this nosebleed should have come as a final nail in the coffin for Gojo, but surprisingly Sukuna too suffered from brain damage due the effects of Unlimited Void and that saved the day for him.