After 6R’ing some tension in the forehead, it doesn’t go away. It even increases. What can I do?

6R it once and Return to the object of meditation.

 You aren’t going to eliminate the headache or tension in one go, but you can Release your attention from it.

If attention keeps returning to that tension, you are basically feeding it, making it stay or even get worse. If you leave it alone, the tension will diminish on its own. Understand that this is just a painful feeling. Use the 6R’s, but only whenever your attention gets drawn to that pain again.