You have smoked for twelve years, which is a pretty long time. It seems that exposure to smoke over such along period has produced chronic inflammatory changes in your throat, which may predispose to cancer. Hence, you should get yourself examined by an ENT specialist
as soon as possible. In addition, you must also consider giving up smoking
. If not, at least cut down as much as you can. Avoid being being with people who smoke. Also instead of smoking the entire cigarette, take one or two puffs and then throw it away. Continue regular gargling.