I'm with Divine. The past relationship was barely a relationship if they had only met once, and the lie is about something honestly not that important considering, again, the relationship he was in barely existed. He's embarrassed which is actually kind of endearing in a way. If the relationship is going well otherwise, don't blow it on something this minor. If this is just an excuse to break off something that is not working anyway, at least be honest with yourself and with him about it.