Yes. DCFS and law enforcement conduct completely separate investigations. An unfounded DCFS finding tells you what DCFS concluded; it does not bind the police department or the State's Attorney.
In Illinois, misdemeanors generally must be charged within 18 months of the incident, and most felonies within three years. Some felonies carry longer statutes of limitations, particularly offenses involving children.
If police have contacted you, treat that as a separate matter from the DCFS case and be careful about giving further statements before you understand your exposure.