The lungs are probably recalibrating as the little hairs that line the lungs take the opportunity to expel the grot that has accumulated over the years of smoking.
Some quitters cough and wheeze others get clear almost immediately. Give it a while but if you are still in doubt get checked by your doctor.
It is now day 8 of my quit and I have found over the last few days that I am more short of breath then I was when I was smoking nearly a pack a day. Fully understand that the lungs need time to clear but I didn't expect that I would be feeling worse rather than better.
It won't end my quit but I am concerned that I have done major permanent damage to my lungs.