Targeting through a single agent may not always be fruitful. Meet a qualified Dermatologist to learn more about the diagnosis and treatment options. Combination of different therapeutic agents is always beneficial. Revlite I.e. Q-switched Nd YAG laser has been available for stubborn pigmentation and can be helpful when topical creams fail. Hope it helps.
Twenty days is too small a time to fix this , however it can be tried or camouflage can be done.
You can contact me on follow up messages for personal recommendations.