What Causes Discoloration Of Skin On Upper Lip On Using Bleaching Kit?

Hi, I had some upper lip facial hair so i tried bleaching it. I used a very mild bleaching kit for facial hair a couple of times. For a while i was really happy because the dark hair was gone, but then i started to notice that my upper lip skin was lighter than my face and i started to worry. Please, it is really embarrasing. What can i do to fix it?