Going by the description that you have mentioned, it seems like a ranula or a mucocele. But the best diagnosis can always be made only after a proper clinical examination. Alternatively you can post the clinical picture on Practo to a specialist for an online opinion. Although this is usually related to trauma and is not due to smoking, I would still like to give you a general suggestion to stop smoking before any adverse effects of tobacco take shape. Also try to avoid playing with the lesion to avoid any secondary injuries which can add to the symptoms.