welcome To HealthcareMagic forum,
Probably you have developed folliculitis
due to procedures like waxing or shaving of leg hair.This then eventually leads to dark spots.
You can apply tretinoin
cream at night over the spot .You can also use combination cream of glycolic acid
at night.These would gradually bleach the marks to normal skin color ,but take long time to work.
If these things don't show good response then you can go for lasers.The best laser would be a Q-switched Nd:yag laser of 1064nm wave length .You might require multiple sessions of the same.
If you can let me know where you belong to ,then probably I can suggest you a laser center for treatment.