I have been diagnosed with post inflammatory hyper pigmentation, what medication should i be taking?

Hyperpigmentation: Once the hyperpigmetation has occurred it will be hard to reverse it, time and protection from the sun will help fade it. Prevention here is key

Bleaching cream?: This will usually subside with time. If this really bothers you a lot, there may be a cream (cortisone/retin A/ bleaching combination) which may reduce the pigmentation.