As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE NOSE GEAR DID NOT RETRACT AFTER TAKEOFF FROM ORD. THE CHECKLIST WAS PERFORMED AND WHEN THE GEAR WAS PUT DOWN IT EXTENDED WITH A BANG. THE AIRCRAFT WAS RETURNED TO ORD WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE FOUND THE NOSE GEAR STRUT FLAT. A FULL SERVICE WAS PERFORMED ON THE NOSE STRUT IAW MM 32-21-02. STRUT LEAK CHECK WAS GOOD.