It most likely is the other tire. I would replace it. If your roads are anything like new jersey roads the belt may have shifted internally from a pot hole. I see this all the time in my shop on all makes of tires, even michelins.
Afe Scoops and CAI, PBX, 261M's Powder Coated Gunmetal, 225/255 Michelin PSS, (BMW Performance: BBK, Illuminated Door Sills, Shifter Knob and Boot, E-Brake Handle, Steering Wheel, Front Strut Bar), E93 FSB, E92 RSB, M3 Rear Subframe Bushings, M3 Front Control Arms, HPA coilover kit (Koni Adjustables and Swift Springs), Steel Brake Hoses, Black Kidneys, Smoked LED side markers, LED angel eyes, Blacklines, Carbon fiber spoiler, Ambergones...