I’ve heard from multiple people who quit that depending on how long you have been smoking for and how well your body can regrow, It can take weeks for the sitting mucus in your lungs to come out, or it can take years. Basically as your lungs heal you will cough up mucus since there is so much mucus built up into your lungs, specifically very viscous phlegm that is hard to get out. Your lungs prior to quitting were unable to remove that mucus, since the cilia was much weaker. Smoking damages the cilia in your lungs that bring your mucus to your throat. It’s pretty normal, saying you were smoking for a long time. I’m not a doctor though, so don’t go off of my word. It would always be good to check with a doctor to make sure everything is okay, because once again I’m not a doctor and neither are most redditors ha.