So is the grinding noise in the axle or freehub?
If it's cup and cone bearing, IMO, it's not uncommon to find them set up ever so slightly too tight. That does cause some grinding noise that you'd only notice when real close in very quiet conditions. It's aggravated even more by bikes with skewers. Not sure about thru-axles.
So might the noise have been there before you changed the cassette?