Removed black matte finish from block next to cable shield
I was swiping my iPhone 4s clean with isopropanol after an earpiece replacement, and carelessly also swiped the black matte finished block between the cable shield and the wifi grounding clip, and managed to remove what appears to be some sort of finish from the block. It is now partly shiny, maybe revealing a film-like surface underneath, but nothing else is "wrong", and the phone seems to function normally. What is that block, and should I be worried? What is that matte finish?