The child was in a restroom stall at the restaurant in the 600 block of North Clark Street when the person entered the stall around 6 p.m. Saturday, police said.
The suspect then battered a store guard who intervened, police said. The suspect also resisted officers who arrived and placed him into custody.
The child was taken to Lurie Children’s Hospital in good condition, police said. The guard refused medical treatment.
Charges have not been announced.