It's a nightmare! You've accidentally posted sensitive personal information online. Even worse, it's already showing up in Google searches.
You can delete the post or contact the owner of the website where you posted and try to have the content taken down. Even if the post is gone, however, it will still show up in Google searches until Google updates its database. There's no telling when that will happen.
For faster removal, use Google's URL removal tool. Just submit the address of the bad content and Google will review the situation. If the case meets the criteria, Google will manually remove the page from its search database.
Google will usually act fast to remove extremely sensitive information like Social Security numbers, bank account and credit card information and images of signatures.
This is a handy tool, but be sure you don't abuse it. Also, read the link at the bottom of the page about when NOT to use the removal tool.
You do need a Google account to make a request, but it's free to sign up.