Why does my chest hurt after running in the cold?

Could be: Sounds like asthma but if this is an acute problem them may be developing an infection. If chronic then ask ur md to try inhaler therapy prior to running to see it helps.

Asthma: Cold air is a common trigger for asthma, especially exercise-induced asthma. While there could be a more serious causes of these symptoms, a primary care physician can help confirm this diagnosis and give you medicine to help decrease your symptoms and increase your ability to run in the cold.

Airways constricting: Lungs that exposed to the cold usually causes a narrowing of the airways, called broncho-constriction. In some cases it may a sign of asthma. Chest pain in general should be taken seriously and may be a sign of underlying heart issues, so seeking medical attention is important.