Welcoem to HCM!
I have gone through your question carefully and it says that you have dull chronic pain
for an year in left arm, upper back and chest, all on left side, with a cracking sound.
From my clinical experince I feel that may be you have an injury
in past in that area. Had I been treating you I would go for an X Ray
neck & chest AP view, along with an ECG . this will tell us about the rib cage
abnormality and any cardiac cause if present. X ray neck will rule out cervical spondylosis
It doesn't look like some thing serious as it has been for an year now and not changed much in nature. So, please donot worry.
Getting your self investigated and taking appropriate pain killer and anti inflammatory drugs will make you good.
It will be wise to see a physician in person at least once.
Hope the answer helps you
Feel free to ask more queries
Dr. Manisha Gopal.