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. So, I'm not sure if second-hand smoke had anything to do with it. On that day, my chest was fine until I did some heavy lifting, where I heaved packages into the back of a truck, along with buckets. I don't know if a muscle strain is a possibility. But I also have this phobia - where every time I finish eating, I panic, thinking food somehow slipped into the wrong wind pipe. But I don't think it would have been food slipping into the wrong windpipe, since I'd assume lodged food crumbs would be more...painful.
I feel like it may be a muscle strain. But I also had breathing issues days before this happened. It could be due to second hand smoke, or the red tide outside. But there were days where I'd be out of breath and would have to take in a deep breath in order to satisfy that feeling. Sometimes, maybe they were too deep, this leads to me developing pain on head, underneath my scalp. It felt quite awful. So maybe there's a build-up of something in my airways, that I am not aware of.
For the area in question, it's around my right nipple, to the right of it. Sometimes, when doing manual labor, a bone near that area, along with some muscle, feels quite tender to the touch and is quite painful. I don't know if it's a muscle strain, build-up of some fluids in my lungs (though I can breath fine, I don't know if there is anything in my lungs), or it's a piece of food lodged in my lungs (I don't think this would be the case, but who knows).