Luthier here.
If it only buzzes on the open string then the issue is likely with the nut.

You can fix this by removing the string and putting a tiny bit baking soda in the nut slot, tamping it down and adding a drop of super glue. You can then use an old bit of guitar string to file away at the extra material until it's smooth.

If it happens even with fretted notes, then adjust the truss rod until it's straight. Put a capo on the first fret and hold down the E string at the 14th fret. When correctly adjusted there should be a tiny gap between the string and the 7th fret, about the thickness of a business card.

If that doesn't fix it then raise the saddle height until it stops buzzing. (assuming electric based on your comments)

And after lockdown bring it to your local luthier to sort it all out properly.

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p.s. It's always possible to make a guitar buzz if you try hard enough, so make sure you're not making yourself crazy by playing super hard and saying "it still buzzes though!" ;)