Your problem could be due to the habit of smoking itself causing irritation of the throat mucosa or due to gastroeasophageal reflux shich can again be aggravated by smoking. If it is since a long time it could also be secondary to sinusitis. Whichever is the case...quitting smoking gradually is needed. Salt water gargles thrice a day will help if it is a simple sore throat. Other conditions need definitive specific treatment depending on the cause.