i dont think its hyperpigmentation it could be a scar or there could still be something in those spots that needs to come out. a few years ago i had a cyst injected it went down but left a red mark that was like a little lump. time went on and the spot never went away so about a year later i went to the derm and asked about the spot. she gave me finacea to use on it and in a few days it became a whitehead which i popped and then it totally flattened out. that mark is gone now but this also happened to another bump of mine on the side of my face. i went to the derm and she said it was scar tissue after looking at it with some special magnifying type of thing she said to use the tazorac on it. i did and a few days later it became a whitehead and i popped it and now its gone as well. so that could easily be it. try using a retinoid on it for a week or two and see what happens.