The village of Tinley Park said the alleged assault happened at Credit Union 1 Amphitheatre on July 22. Wiz Khalifa and Sean Paul played there that evening.
The investigation began on July 24 after hospital staff in Ohio notified Tinley Park police of the incident.
Investigators collected surveillance footage provided by Live Nation, witness statements and a forensic interview. The Indian Hill Police Department in Ohio helped collect additional evidence.
Authorities learned that the suspect, Roman Basso, an 18-year-old Frankfort man, was enrolled at Arizona State University. ASU police helped Tinley Park detectives find Basso, who was taken into custody in Frankfort on Tuesday.
Officials said Basso confessed while in custody. He has been charged with aggravated criminal sexual assault/bodily harm, a class X felony.
Further information was not immediately available.