"Mmm." Jack grinned, arching against Spike. "Not yet." They were beginning to ache, but not enough for him to admit to pain. He turned his head enough to look at Ianto, blinking in surprise at the marks. He wanted to ask how Spike had managed to get Ianto to let him do that, but he could see the warning in Ianto's expression. The question could wait.
Ianto turned slightly so the bite mark was less visible to Jack, leaning one shoulder against the wall. After this, he would have to make sure to avoid Jack, because he was not going to have him ask questions about it, and once he'd had a chance to return home, he'd forget about it. Both of them would, and it wouldn't matter any longer.