Wondering why would smoking less cause lungs to hurt?

When we stop smoking: Our lungs are finally able to start cleaning themselves of all the crap we put down there for years. This can result in the development of a severe cough in many people, and coughing can cause pain. However, this is actually a good sign and means that you are starting to heal, and it generally will get better after a few weeks. Try to quit completely and do your lungs/heart a big favor.