It is just a habit and you can get rid of it simply by becoming conscious and ignoring when the urge arises. Or else you can form a contrary habit that is not harmful, for example, holding a ball in your hands as you undertake different activities. Concentration develops with practice. You could start with concentrating on some physical work at hand or else on a picture of the Mother. Certain games like Carrom and Mikado also help develop Concentration.
Affectionately,
Alok Da