This is probably easier done in Photoshop since there you have much better and accurate selection tools, but I guess that's not what you want to hear, since you specifically asked how to do this in Lightroom.
The most accurate way of selecting an area to work on in Lightroom is using the paint brush, make it very large (so it covers more than the bright spot you want to work on), select "Auto Mask" and click once in the bright spot. Then it should theoretically select all similar toned areas under the brush and leave the darker toned areas alone. After that you can use the sliders in the brush to adjust to your liking.
In my experience this works best with sharp outlined areas, as soon as you try to do this in an oof background you start getting strange halos around the spot you're working on.