My technique to remove the excess spill light on the forehead.
1. Duplicate the image layer and change the blending mode of the duplicate to Hard Light
2. Use the Burn tool to darken the unwanted spill light. Begin with the tool in the Shadow mode and work from the inside toward the "rim" lighting. Use the tool at medium opacity to build the effect slowly.
3. Repeat the burning with the tool set to Midtones and then to Highlights until the desired effect is obtained.
4. The Hard Light blending mode minimizes some of the desired rim lighting in other areas, so add a layer mask to the duplicate layer and use a black brush to restore those areas.
For me, using the burn tool leaves more realistic lighting detail than attempting to use the brush tool.

forum discussion: http://forums.dpreview.com/forums/read.asp?forum=1006&message=40569737
original image by kuttua: