During a fight against a special grade curse, Yuji loses his left hand. He’s seen with it for the rest of the series, so how does Yuji Itadori get his hand back?
Yuji Itadori is able to get his hand back after he lets Sukuna take over. Sukuna regrew Yuji’s hand while trying to deflect an attack from a special grade cursed spirit. The hand remains healed even after the fight is over.
Sukuna was able to regrow Yuji’s hand thanks to his super high level of cursed energy. He didn’t mean to heal it, and did so by accident. Later, Yuji is instructed by Gojo to watch movies in order to have better control over his own cursed energy.
Sukuna helps Yuji get his hand back
At the end of chapter #7, Yuji hears a howl from one of Fushiguro’s dogs. The howl is the signal that Yuji can turn control of his body over to Sukuna, as everyone else is out of the building and safe.
He lost a hand in the fight against the special grade Finger Bearer cursed spirit. At the start of chapter #8, Sukuna has fully taken over control of Yuji’s body.
Sukuna realizes that if he chases after Fushiguro, then Yuji will likely just swap places with him. The best course of action is to lure the cursed spirit to the sorcerers, that way Yuji can’t switch back as long as he needs Sukuna’s strength.
The special grade doesn’t seem to respond to Sukuna’s proposal. Instead, it launches an attack on him. Before it can make contact, Sukuna uses his cursed energy to regrow Yuji’s left hand and deflect the attack.
“Oops,” Sukuna says, “I fixed this too.”
So that’s the answer. Yuji Itadori was able to get his hand back after switching places with Sukuna. A high level of cursed energy helped Yuji’s hand grow back while Sukuna was deflecting an attack from a special grade curse.