You might have a medical condition named acanthosis nigricans. It can sometimes cause the lower face to be darker than the rest. It's not dangerous but could be a sign of something more serious, like insulin resistance, that is happening inside your body. You can fix this by eating cleaner, being active, and maintaining skin health. Furthermore, consume a lot of water. 

You may be having a skin disorder known as vitiligo. Vitiligo is a condition in which parts of the skin turn white due to a lack of pigmentation. Problems like the skin shortage of pigmentation appear in white patches due to vitiligo disease. The methods of treating vitiligo can be quite difficult, but they can be handled with the help of some medicines like calming creams, phototherapy, and sometimes surgery. Not using sunscreen and the nervousness of a greater cause can intensify the symptoms. Visit a dermatologist for diagnosis and treatment.

If it has turned slightly yellow, it may be a minor infection. Using Boroline is fine at the moment. When it is discharging clear liquid, then it is healing. Do not pick it, keep it clean, and look for any redness or increased pain. It will get better in about a week.