The Doctor sat for minute processing that. He hadn't actually had a chance to have a good talk with the Master today, just a "Hey, see you at the party." Clearly he'd been missing a lot, in the last few days.
"I'm not sure how you want me to respond to that. We've not discussed what obviously happened between you, at all. We've been busy. I'm not angry or jealous. A little thrown. So, not a good experience? Do you want to actually talk about it?"