If there's nothing growing in it, I wouldn't worry. Just be sure to fully drain it when you're done brewing with it before putting it away. I'd also leave it open so that it can dry out inside.
Generally speaking, you don't need to sanitize anything before the end of the boil. Post boil (or chilling of the wort) you want anything touching it to be sanitized (and clean). Clean is critical pre-boil though.