Zoom in on the problem area. You want be close enough that you can see the area clearly, but not so close that you can't see the colors of the big picture.
Select your burn tool, it is shaped like a little hand. If you have another tool in the area of the burn tool, such as a little sponge, you will need to right click on the shape and change the menu to the burn tool. You will then need to select your brush size. I like my brush is be pretty small, about a 12. Then select your range, if the problem area is really dark, then select shadows. Set your exposure about 50 percent, this will make the burn less noticeable.
Then you should have either a vanished booger or one that is extremely less noticeable.
How about your family, is this a problem you run into a lot?