You haven't mentioned what kind of mark is it?
If it's a birth mark, then you need to opt for LASER
In case it's an acne mark/ injury mark or any post-inflammatory hyperpigmentation, you can take homoeopathic medicines - Berberis Aquefolium Q/ 10 drops in 1/2 cup of water and Kali Brom. 200 - both thrice daily for 20 days.
Revert me back there after.