You will have a few withdrawal symptoms If you can cope up with them and your resolution is strong enough eventually you will go through that However if the symptoms of withdrawal are significant you should consult a General Physician or a Psychiatrist.

Hi there...I can understand your concern for your friend. It is good that he has decided to quit smoking. There's no harm in suddenly quiting to smoke cigarettes. Only problem is, since it is a chronic habit, he might find it difficult to quit it suddenly. He will have the urge to go back. So it is better if he takes a help of psychiatrist. They will be able to councel him and help him better. So also him to consult psychiatrist if he is having difficulty in quiting to smoke.