Some haloing is natural, that’s simultaneous contrast for you.
My experience is that a group of digital imaging pros is a lot more finicky about this than the client base as a whole. I don’t know how many times I’ve heard halos being condemened as amateurish and unacceptable, when the client never realized anything was amiss.
If you decide to reduce wide halos (there's never a point in getting rid of them entirely) remember that small interruptions in the pattern disrupts the viewers perception that there's a halo, so you don't have to attack every part of the halo.
The halo usually falls between a light and a dark object. Assuming that the light object is everywhere lighter than the dark one, the solution is easy, set the rubber stamp tool to 50% (or whatever) Darker Color mode, option-click just outside the halo in the light area, and then paint right over the halos. You don't have to be careful not to brush over the darker object, since you can't change it when the brush is in Darken mode.
If that's impossible because the light area is mottled or whatever, I'd make a rough selection of the area needing to be filled, plus a bit more of the light neighbor and as small amount of the dark one as time permits. Then, on a duplicate layer, Average, add Noise, add a black layer mask, set layer mode to Darker Color 50%, and you should then be able to quickly paint over the halo areas in the mask. Again, this can be done very quickly as it is impossible with these settings to damage the dark object even if you paint over it.