If you have cancer of the vaginal canal, will smoking worsen it?

Yes. Smoking decreases your body's ability to fight cancer-causing virusal infections. Smoking also impedes healing of tissues involved with surgery of excision of vaginal cancers. Smoking can only make the problem worse...And is a risk factor for recurrence.
Vaginal CA & Smoking. Smoking is, as you already know, a risk factor for vaginal cancer. But, i assume you have had definitive surgery and treatment for it. While smoking can contribute to a recurrence, the far larger problem is that smoking is a risk factor for lung and other cancers. Now would be a good time to wean yourself from the habit.