He was struck by Boruto himself!
Warning: spoiler alert!
It looks like karma has finally reached Sasuke in Boruto: Naruto Next Generations. After losing an arm to the Otsutsuke clan, the ninja suffered an eye injury in chapter 53 of the manga. In the last issue, we saw that there was a strategic objective for this attack.
Who hit Sasuke with a kunai was Boruto himself. Momoshike has taken complete control of the young ninja’s body, part of his plan to extract the chakra from the planet.
His target was the Uchiha’s left eye, his Rinnegan, to prevent him from using his dimensional manipulation skills. This ability proved essential in the battle against Isshiki and that was exactly how the group intended to escape if things got too complicated.
With nowhere to run, the only option for Sasuke and Kawaki is to fight, even if they have to kill Boruto in the process. When Momoshike hits Kawaki, he eventually realizes that even without the mark of karma, the ninja’s body has already been 80% transformed into Otsutsuki.
He then shows his sadistic side by treating Kawaki as nothing but food to transform the ten-tailed beast that lives in Isshiki into the divine tree chakra fruit.
In the midst of the battle, Sasuke realizes that Momoshike can only suppress Boruto’s consciousness because his body is completely devoid of chakra. After many fiery jutsu and a suicide bombing by Kawaki, they manage to banish Momoshiki into Boruto’s subconscious, getting his friend back.
Without Sasuke’s dimensional powers, Boruto and Kawaki will have to appeal to their dark side of Otsutsuki if they are to break out of this dimension. But will Naruto survive this trip? The way is to keep following the manga!