Eat ice cream fast, and your forehead can ache, even though the cold touches the roof of your mouth.
Researchers think chilling that spot quickly makes tiny blood vessels narrow, then swell wide as they warm up again. Pain sensors there feel the swelling.
They signal the brain through the trigeminal nerve, which also carries pain from your face, including your forehead. The brain misreads where the signal began, so you feel it there.