Try calling the Lincoln Minimum Housing Code office at 402-441-7521. It is unlawful for a landlord to rent an apartment or house that does not meet the standards of health and safety established in the Lincoln Minimum Housing Code (Chapter 21 - Lincoln Municipal Code).
The Housing Code Office is the city agency responsible for enforcing the Code. Call the Housing Code Office and ask an investigator to come to the apartment and examine the problem. If the apartment is not in compliance with the Code, the investigator will outline specific steps the landlord must take to make the repair, and the investigator will issue a deadline for compliance.
If you have a problem related to mold or mildew or other health-related issues, contact Lancaster County Health -- Environmental Quality at (402) 441-8000.