As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, RETRACTED GEAR AND RECEIVED NOSE DOOR WARNING MESSAGE. RETURNED TO FIELD. VISUALLY INSPECTED NOSE LANDING GEAR DOOR PROXIMITY SWITCHES AND NOSE LANDING GEAR DOOR WARNING SYSTEM. PERFORMED SYSTEM TEST OF PSEU REF CRJ FIM 32-60-05. COULD NOT DUPLICATE DISCREPANCY.