Why does spicy food cause mild pain or hot sensation when the food isn't temperature hot?

This might get you looking in the right direction.

It has to do with your tongue , taste buds and the chemical in the food / spice . Not everyone senses the same heat level from the same dish .

It’s a language shortcoming.

Most other languages have separate words for “temperature hot” and “spicy hot.” English has only one.

The human brain cannot measure exactly what the sensation is when the nerves are excited by it, other than it is an irritant so it uses heat to describe it. the brain is an amazing tool, but as any experiment with a blindfolded person proves, there are certain shortcomings when it comes to sensations.

Blindfold someone, tell them you are going to drip hot candle wax on them, and then drip warm water on them instead. If they are convinced it was wax, they will cry out in pain. I know, I’ve conducted this experiment on folks in the past. I was a torturer during the Spanish Inquisition.