No matter what your cravings are, you need to try your best to avoid them. You need to try your absolute hardest to keep your word, especially since you swore in the name of Allah, the one who created you. If you truly fear Allah, don't take the risk. As we are only humans, we can't say you will or won't be forgiven, as that knowledge is only with Allah SWT. And everything is judged by your intentions, so if you know what you are doing is wrong and still do it, it is worst than for someone to do something wrong and then realise after that what they did was a sin (and Allah knows best).
"Allah does not impose blame upon you for what is unintentional in your oaths, but He imposes blame upon you for what your hearts have earned. And Allah is Forgiving and Forbearing." 2:225
Besides not smoking because you swore in Allah's name, you would have also lied to your mother, who at her feet lies heaven, and so if she doesn't want you to smoke then you shouldn't, especially not behind her back.
Besides all this, I know there are a lot of controversy regarding the status of smoking, but we all know that it harms our body, and we also know as muslims we have been given our body as an Amanah for Allah. In other words, our physical body isn't actually ours. It's been given to us as a mercy from our lord, and our duty to it is to take care of it as much as we possibly can. If you gave your friend a car to borrow for a while, you would want them to take care of it in the best possible manner: to give it the right fuel, to wash it regularly, to keep it tuned, to keep it away from the possibility of being damaged in any way. You would want them to return that car to you in the exact manner that you gave it to them, because you trusted them with it. Our body is similar. You need to try your best to take care of your body in the best manner possible, and not to damage it when we know we are damaging it.
I know I have made this more of a lecture than an answer to your question, but consider this for the better, InShaAllah