The Country Music Hall of Fame and Museum is a worthy visit, and you should go check out Gruhn Guitars & Carter Vintage just to see the incredible inventory.
Some of my favorite restaurants:
Husk
The Southern
Kane Prime (pricey, but about best steaks in town)
Puckett’s Grocery (more of a meat & 3 type deal with live music, usually…several locations)
The Grand Ole Opry tour is fine if you’re a big country music fan. If you can get on the tour that happens during the show, that’s pretty neat as you’re able to see a bit of the hustle & bustle backstage. Attending the show itself is really fun.
Also try and check out a show at the Ryman. If you’re there on a Monday night, do your best to see The Time Jumpers perform at the venue called 3rd and Lindsley: https://www.3rdandlindsley.com/
You can buy your tickets beforehand online and then arrive early for seating. They are a Grammy winning western swing band that is pound for pound the best band configuration in Nashville, dare I say.
And, of course, check out what’s happening at The Station Inn: https://stationinn.com/events/