That little nub is a soft steel rivet that needs to be pulled out. If you just grind it off there’s a remote chance the rest of it could drop into the bearing. If you have a sharp pair of vise grips or a milling vise you can grab it and pull it out.
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience