if the goal is to recut/remove that ding, it will be far more complicated and expensive that just a touch up.
There is no such thing (a touch up)... if you can see it, it is several thou deep and if you ream that much, your headspace is now out of spec. So you will need to set back that barrel.
This assumes, the gunsmith reamer is an exact match to your chamber. If not, you need to set back until both dimensions match or you will end up with more ridges and rings to enjoy.
So to fix, the cost will be similar to setting back a chamber and just as complicated.
As long as the brass is not cut, or held in place (hard to extract), or at any risk of splitting/damage, I would lean towards enjoying the barrel for what it is. Certainly not the first barrel with a ding (think of the thousands of milsurps in service still).
But, let your conscience be your guide.
Jerry
Jerry