I have an image with a black smudge of dirt on the model's palm - still not sure if that'll be one of the variants I use - however it got me thinking about retouching tricks to remove it. It was a result of her grabbing a dirty metal bar, so she's got a black smudge on her palm. I can't post the photo, but I think everyone has seem a smudged palm from grabbing something dirty. Kind of a black smudged soot.

The usual suspect occurred to me of course - cloning. But there is always some cool unsuspected trick with photoshop for things like this - so I thought I'd ask.

its called the dodge tool (looks like a magnifying glass or Lollypop icon)
then put it at 6-9% on a soft brush and setting in 3 section window (Highlights / Midtones / Shadows)
put it on "Shadows" then brush over the area gently ... this should remove the black.

REMEMBER to always make a copy layer to test on first.

I think dodging my work if the mark is relatively thin and the underlying color is still visible. If it is dark black then dodging by itself will be ineffective. It would help to know how much of the palm surface is affected. A small area and the clone stamp is probably still the easiest but if you are rebuilding a large area the difficulty will be in recreating the natural crease lines and shadowing.

I'd suggest to clone over it and then dodge and burn if needed to even it out.