As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD INFLIGHT - DURING GEAR RETRACTION AFTER TAKEOFF HEARD LOUD AIR NOISE AND FELT VIBRATION FROM NOSE GEAR AREA. CYCLED GEAR WITH NO CHANGE. RETURNED TO ORD AND LANDED WITHOUT INCIDENT. FOUND NOSE GEAR DOOR IN OPEN POSITION. ADJUSTED LEFT FORWARD DOOR LINK. SYSTEM GROUND CHECKED NORMAL OPERATION.