Nope, that wasn't a sprain. The kid was in pain too, and it didn't take a genius (which was a good thing, because Jiraiya was no genius) to figure out that it was some more of that weird island bullshit.
"Don't." he said, giving the kid a serious look. "Don't ask to do her favors, that's how I got into this mess. I think. Actually, it's your fault. You're the idiot who smashed up all the mermaids." He was grouchy because he was in pain, but he'd have been grouchy even if he wasn't, so there really was no excuse. "There's mermaid bits all over the front of this giant suit. Why the hell do you need something this big anyway? Seems like a load of trouble to me, what with smashing up the scenery and all."
He had long since mastered the art of grouching while in pain. It was a lovely coping mechanism.