You have two options, you can layer a high hydroquinone cream like caro white on it since it absorbs/dry into your knuckles very fast then apply your neoprosone gel or cream.
Option 2
Or If you have access to peels and want faster result, you can do a glycolic acid or lactic acid peel every night for a week and then layer your carowhite / neoprosone gel cream on it.
The best way to apply the creams is to put it on the tip of your finger and rub it on your knuckles
Something like this
Apply an ample amount when applying the neoprosone gel and caro white cream