That cloudy white circle in the center of a worn patch is the hydrocolloid material itself, saturated with absorbed fluid. Hydrocolloid is a polymer that turns into a gel when it meets moisture, which is exactly what it's designed to do — absorb fluid and oil from a surfaced spot and lock it into the patch. So that white spot isn't the pimple coming up through the patch, it's the patch saying it's done its work. Once you see it, swap to a fresh one if the spot is still present. If the patch stays totally clear after several hours, the bump may be too deep for a hydrocolloid patch to absorb.