Leukoplakia white patches. Appointment?

I am having a white patch in one side of my cheek. I addressed it while resuming my smoking habit. I had a habit of chewing tobbacco 8 years ago for 3-4 years. I quit that and started smoking. Used to drink alcohol on moderate basis for 2-3 years. The patch is on one side, white one. I went to a dentist and he said its a localised one and gave me vitamin A tablet for one month and prescribed excisional biopsy. I quit smoking 1.5 months ago. Still the white patch is not reducing. Its not paining while eating, but its giving me stress as it can turn into a cancer in future. I am only 31 and getting married. But this patch giving me enough fear. Can i go for a biopsy in the next appointment? Please give me suggestion DRs, i will quit everything and i want to leave a tobacco free life now. Please help me.