To put things into context, I work for delivery/repair. I'm still in training, so I tend to be paired with smokers. I don't know if second hand smoke is the cause of this, since I work 2-3 days for week, at the moment. But the training routes take a couple of hours with them, thus being exposed to second hand smoke.
However, this feeling where I feel a slight pop, depending on how I breath, didn't start until a few days ago.