Nicks don't help, they can add to cavitation. You don't say what motor, but the higher the HP the more critical for a smooth edge. Some carefull filing will clean that up. What's more critical is the end that almost rubs the wear ring. With a new wear ring it should literally just clear if not slightly rub on the ring. If it's worn so there's a gap of even a 32nd of an inch it will cavitate on higher HP motors. Can't tell the ring to impeller clearance in a picture.