“An operating system wasn’t found” After Boot Camp.

I have a serious problem that I don’t think is fixable. I was recently installing Windows 10 on my Mac Mini (Late 2012) model and I managed to boot into the Windows setup menu. It said “Windows can’t be installed on drive x partition x”. I watched a YouTube tutorial on how to fix this problem and it didn’t work. They made me clear out my both my internal hard drive and external SSD drive which I was stupid enough to do. I rebooted my Mac and held the ‘alt’ key and all I saw was ‘Windows’ and ‘EFI Boot’. My MacOS wasn’t there. So I went into the Windows setup menu again and encountered the same problem (Afterwards I disconnected my USB Flash drive which was I think why it ruined it). I kept rebooting my Mac and all I would see is “An operating system wasn’t found. Try disconnecting any drives that don’t contain an operating system.” No matter what I did it would go to the same exact screen. I tried booting into recovery mode and it just brought me to the same screen, this was the same with Startup Manager. I really don’t think there is a fix for this but if anyone can provide any help that would be greatly appreciated.