Post Inflammatory Hyperpigmentation (PIH) does not always occur. It is a result of increased blood flow to the affected area, resulting in a stimulation of the cells that produce pigment.
PIH is more likely to occur in darker individuals. It does not incur for all injuries. If your acne was particularly large and swollen or if you were exposed to a lot of sunlight during this period, it is possible that an overstimulation of your pigment cells may have occured, resulting in PIH. Squeezing it will result in increased blood flow and not only worsen your acne, but will leave you with an increased chance of developing PIH.
When left alone, PIH can fade over time. It may take sometimes up to 6 months or it may never actually fade completely. The process of clearance can be speeded up using either a Q-swtiched Nd-YAG laser or a Picosecond laser to help break up the pigment and allow for the body to clear it out faster. I prefer the latter. You can also use creams that contain hydroquinone and retinol combined in order to suppress pigment formation and push the current ones closer to the skin surface for it to eventually flake off.
