Yes you should stop smoking. Your cold may go away normally but the very aggravating cough could linger for a couple of months due to the tobacco use. I don't know much about marijuana but I would think that inhaling any type of smoke into your lungs is not a good thing.
Usually a week or a little more is average for a cold. Smoking Pot is actually worse for your lungs. Smoking tobacco and Pot is a double Whammy on your lungs. You are being self-abusive, how come?