IMO there's nowhere near enough damage to cause any kind of a problem. I'm assuming from the picture that the blackened area is just a bit of surface burn from applying heat. File the edges of the nicks to make sure the bearing and seal slide on smoothly and carry on. I've replaced a boat load of wheel and shaft bearings over the years, some with spindle damage worse than that, and had no issues afterwards. Keep in mind that those nicks represent maybe 2% (I'm guessing here) of the total seating area. If 98% doesn't do the job then 100% won't either.