Habits maybe difficult to get rid off. You must ask yourself whether it is really bothersome in any way. Also what triggers it off? Is it boredom/stress/anxiety or is it self-soothing? Once you are aware of the reason you will be better able to deal with it. If it is like a compulsion, as if you are unable to control it and it consumes a lot of you time, leading to distress it maybe a good idea to consult a Psychiatrist to get evaluated for Obsessive Compulsive Disorders (OCD).