Secure Boot Violation, Invalid Signature Detected. Check Secure Boot Policy in Setup

My home/personal PC “Dell Inspiron 3656” has an issue. I can’t boot!I get a black screen with a red error box. In the red error box it reads “Secure Boot Violation, Invalid Signature Detected. Check Secure Boot Policy in Setup.”I can’t get past that. I have been in/out of the bios screen and made some alterations to the boot options, but still, nada.I followed some youtube videos and came up short. Some changes worked for other people, but not myself.

I didn't make any recent changes to my PC either. Nothing.

Any help? Advice?