system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is pain amplified when the temperature is lower?
gpt
The nervous system has a threshold for pain.  If someone brushes your skin, that contact doesn't come even close to the threshold over which your nervous system decides that something hurts.

So basically, things hurt more when it's cold because the cold external temperature is already stressing your nerves.  Feeling cold can be considered a form of "pain," so when something additional happens- say, you stub your toe and your feet are already cold- it not only crosses the threshold of "sensation vs pain", it ROCKETS over the threshold.