Shite. That sucks.

Can you share more about the symptoms? You say "it does not get past the Nintendo logo." Do you mean the "Switch" logo? What's it do when it gets to the Nintendo logo? Hang on the logo forever? Does the screen go black after a second or three? If the latter, after the screen goes off, does the power button repeat the performance, or do you have to hold it down for a while (to shut it down), let go for a sec, and hold it down again to make it boot up again before it responds?

You can of course send it to Nintendo to get it fixed. That's probably your best bet.

But if you can't or don't want to go that direction, you might be able to resurrect your system with homebrew/hacking. That'd require getting set up to hack your Switch, though. And might void your warranty.

First thing I'd try if you want to go that direction is to just run Hekate (a fancy homebrew bootloader for the Switch) and boot into Atmosphere via that. No need to set up EmuMMC just for that test, but there is some risk of getting banned from the eshop and online play if you make any changes to your Switch (like installing pirated games, for instance) and then connect to the internet.

It's possible something went wrong with the efuses on your system and your Switch isn't starting because it thinks you've hacked it and manually downgraded the OS even though you didn't. I believe Hekate and Atmosphere would let you boot into your Switch's OS in a way that would make your Switch ignore any efuse discrepancies. Might get you past the issue you're having.

But again, there are some risks with this approach and if you're wanting to get it fixed by Nintendo, I'd say probably your best bet is just to send it to Nintendo.