As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING INITIAL CLIMB AFTER TAKEOFF AT APPROXIMATELY 300 FT AGL, CREW RECEIVED MASTER WARNING AND FUSELAGE DOOR LIGHT. CREW COMPLETED INITIAL CLIMB TO 3000 FT. CREW SAW IT WAS THE REAR CARGO DOOR INDICATION ON THE DOORS PAGE AND RETURNED TO LAND AT EWR WITH NO FURTHER INCIDENT. FOUND HANDLE PROTRUDING, RESET AND OPS CHECKED GOOD.