You should consider contacting an attorney. One of the most difficult hurdles for claimants to clear in a pemises liability case is proving that the property owner or manager knew about the dangerous condition. It sounds like your friend provided notice of the dangerous condition prior to your fall. The complex should have acted on your friend's report and repaired the damage prior to your fall. Talk with an attorney as soon as possible so evidence can be preserved, statements can be obtained, and other investigative step can be taken. Good luck.
If your friend reported the broken steps to the apartment manager prior to your fall, that will greatly improve the likelihood that you can prove the apartment management had actual knowledge about this problem. These matters are best handled by an experienced trial attorney, such as one who is Board Certified in Personal Injury Trial Law.
I would recommend that you get pictures of the broken step, report your injury to the apartment manager or front office, and get to a doctor as soon as possible to examine you. Good luck to you.
My responses to questions on Avvo are never intended as legal advice and must not be relied upon as legal advice. I give legal advice only in the course of an attorney-client relationship. Exchange of information through Avvo's Questions forum does not establish an attorney-client relationship with me. That relationship is established only by individual consultation and execution of a written agreement for legal services.