。
If you're going to apologize, sooner is better.
Literal
Apology [object-を] put-in [conditional-なら] early side [subject-が] good [conjecture-だろう].
わびをいれる (to apologize, literally 'to put in an apology') is a set phrase, slightly more humble and formal-feeling than 謝る. ~方がいいだろう combines the comparative ~方がいい (better to) with だろう (probably), making it a gentle suggestion rather than a command.