can't get into dashboard – 500 server error

Not sure what happened. Haven’t done anything different or added anything in awhile. I’m obviously logged in and from my site I can click on dashboard but then I get the blank screen that says server error. I click more and it give me this: The website encountered an error while retrieving https://www.shugashug.com/wp-admin/update-core.php. It may be down for maintenance or configured incorrectly.
Error code: 500

I’m a complete newbie so thanks in advance for all help. I”m using bluehost right now.