Yes the but damage from rasenshuriken wasn't from him hold it, it's from when it exploded. I don't remember rasengan ever hurting Naruto's hand.he still holds the rasengan while hes creating it like i said a few comments up he holds the rasengan just like when he first was learning the rasengan from J-man it hurt his hands then when he used rasenshuriken for the first time it hurt his hand so thats is why im saying it might have been a training accident