Thanks for your question on Health Care Magic.
I can understand your concern.
Since your ecg is normal, no need to worry for cardiac cause. You are mostly having lung inflammation because you are smoker.
Cigarette smoke causes persistent inflammation and irritation in the airways. These cause soreness and itching in the airways.
So better to quit smoking as soon as possible.
Get done PFT (Pulmonary Function Test) to rule out
bronchitis as this can also cause similar symptoms.
If PFT is normal, then only
smoking cessation is needed to treat your problem.
You should enroll in deaddiction center. Start
psychological counselling about deaddiction. Don't worry, you will able to quit smoking.
Hope I have solved your query.
Wish you good health. Thanks.