It's hard to resist the urge to just release the staged repository (it's only a click away), but as suggested in the Sonatype OSS Usage Guide
You will want to download them and do some manual testing (or hold a
community vote) before finally releasing them.
If it's the first time you've released, then you'll have to comment on your OSS Sonatype JIRA ticket to get Central synch activated. Presumably this is an opportunity to say "Wait! This artifact is broken. Please please please don't synch it to Maven Central!" :)
But as others have said, if it's released then it's too late - you'll have to release a new version (and ensure your users are aware not to use the broken one).
Beta releases are a good idea for new/major releases - people are a bit more forgiving if you've stuffed something up, and you don't lose your desired version number.