I had a mechanic service my motor and change out the impeller. He couldn't get the plastic and stainless collars that holds down the impellar on the shaft off. So I saw him hitting it with a screwdriver and hammer. He put these nicks in the shaft under where the plastic and stainless rings sit.. Is this something I should worry about? Or would maybe just smoothing it out be ok? Or is that something to worry about to were I should make the guy replace the shaft?? could the impact of him hitting the shaft had messed it up to were it could cause a wobble in the motor or mess up any seals?