If you didn't try to log in and your account locked anyway, that means someone else may have tried to access it. The good news: the lockout did its job and stopped them.
Contact support right away. We'll look into the activity on your account and make sure it stays secure. While we're investigating, don't try to log in yourself — and once your account is accessible again, plan to reset your password as a precaution.
Some general security steps that help in any situation like this:
Change your password on any other accounts that share the same or similar credentials
Turn on two-factor authentication anywhere that offers it
Watch your bank account for anything you don't recognize