"I'm sorry," says Paul, taking another bite of his own cake, blushing as he looks away. Absurdly, he wishes he was still holding her hand. "For staring. I wasn't raised to be so rude."
Other options:
no subject
"I'm sorry," says Paul, taking another bite of his own cake, blushing as he looks away. Absurdly, he wishes he was still holding her hand. "For staring. I wasn't raised to be so rude."