I don't think your boyfriend would have said this to hurt you. Boys can be insensitive without realising it.
He could have thought that you were perhaps meaning other girls in your group, but when he saw the look on your face, realised it included you and tried to make up for it? I dunno, I wasn't there *shrugs*
Remember, looks aren't everything! There's also personality. He's going out with YOU, not her! Surely that says alot? If he didn't want to be with you, he wouldn't be.
And by giving you an honest answer, it shows he's comfortable around you, and feels he doesn't need to lie.
These are just my thoughts on the subject, so could be wrong. If it really bothered you that much, tell your boyfriend... I'm sure he'll wanna know if he's hurt you so he won't do it again?
Luv Claire