Throat and lung irritation. Infection?

One day I smoked more cigarettes (normal 1-2 in a day and that particular day i smoked 4 cig in 2 hours) and am having throat and lung irritation and my inner lining of throat have reddish lines now which i guess is infected and the doctor prescribed me one cough syrup and antibiotics 650 mg but I am still having the irritation even after 5 days of course though the redness has decreased and I don't have jaw pain now and the doctor says is throat infection because of which there is cough that has accumulated in the lungs which will take time to clear out and he has asked me to stop smoking so I have left smoking now forever. And whenever I cough (which is quite rare even after the infection) I see white color phelgm with small black particles. So can anyone suggest me what should I do? Do I need to worry a lot about it or it looks like a simple infection? because I think a lot about this and It's affecting my studies now. Kindly help Sir/Ma'am