How deep is the scratch? Beyond the clearcoat? As said, it will catch on the fingernail if it is. Those are the gloss plastic B pillar and notorious for picking up scratches and swirls, as plastic always marks more easily than the bodywork. As suggested get a DA on it with a suitable compound and pad (combo will depend on nature of scratch but best to start with least aggressive and work up as needed),and if it's not into the clearcoat it should come out. Even if it is into the clearcoat you can lessen the appearance with the DA as it will soften the edges of the scratch, then maybe further disguise it with a glaze such as Poorboys Black Hole which contains fillers to mask light scratches and swirls. B Pillars often need a few polishes a year to keep marks at bay.