It could be the action is too low. It could be the nut is too low. Or just that slot on the nut. Or the nut could be cracked.

First thing I'd do is raise the bridge saddle on that string a bit to see if that solves the buzzing.

You might consider taking it to a guitar store you know & trust, if that's an option.

You are also welcome to ask our resident GT tech for his more professional opinion!

https://www.guitartricks.com/forum/threads.php?f=30