If the stain is still there when you put the garment into the dryer, you will risk setting the stain. Try to remove the stain again. If you can't, let the garment air dry, and take it to a professional dry cleaner.

How would you rephrase that briefly using Vietnamese?
Đảm bảo vết ố phải sạch hoàn toàn trước khi sấy.