Spike's sensible to be worried: after this, Jack is far more likely to push for more biting in the future! He'll try to respect Spike's feelings on the matter, but in the heat of the moment he's likely to bring it up.
He watches Spike lick his blood off his fingers and while it might be gross to some, to Jack it's just hot. Kinky and hot. He smirks a bit, because it's obvious what Spike's considering and he's always happy to give head if that's what Spike wants, but he's equally happy to just let it go from here. He lets out a breath and looks about him, at the dark corridors that have been the setting for so many of his nightmares.
"Well, I'm certainly never going to look at this place the same again!"