Mouth ulcers take upto 7 to 10 days to completely subside. To speed up healing you can take high dosage of vit c chewable tablet limcee and b complex like becosules. Also can apply hexigel to the ulcer . If these are recurrent ulcers then most common cause is stress. Or if it's happening in one particular area it may be due to local irritant like a sharp tooth .

We need to know the etiology, that is the causation! Whether the drugs themselves or causing this or is there an underlying condition. Then only a suitable treatment could be provided. Use dentogel, a topical anaesthetic for temporary relief