Pain in forehead during cruise only - after a cold

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I have had quite a bad pain in my forehead whilst sat in the cruise - gradually gets worse during climb and eases in descent - just about back to normal on the ground.

I have been suffering a cold and have recovered - I can clear my ears no problems and have no problem at all on the ground.

I'm guessing its some trapped air in my sinus (just above my nose) but any ideas how to get rid of it? I'm typing this message sat at home with no problems and no pain.

Been sat in the cruise at 36000ft this evening - approx 7000ft cabin altitude.

Ideas????

Thanks.