It's fine, forget it. More importantly, if we don't hurry, the time sale's gonna end.
Literal
Good [explanation-のよ]. Than-that, quickly go-[if-not-ないと] time-sale will-end-up-ending.
いいのよ chains the explanatory の with feminine よ for a reassuring 'it's fine, let it go.' それより is a discourse marker meaning 'more importantly / never mind that' — literally 'more than that.' 行かないと is an abbreviated conditional: the ~ないと form is equivalent to ~ないといけない ('have to'), with the 'if not' consequence left implicit. 終わっちゃう is 終わってしまう contracted — 'will end up ending,' with ~ちゃう flagging the speaker's dismay at the imminent outcome.