When my son was around that age he told me that a man pulled down his pants in nursery school. He said it in a very offhand, relaxed manner but it sounded like something to check up on. I remember that I gave him a bath that evening, in large part to see him naked without attaching any special motive. Everything seemed fine. I asked about it casually at bedtime and he repeated his original statement.
Now he went to nursery school half days primarily to give me some one on one time with my new baby (he was my middle child). The school was a kindergarten through eighth grade school with two years of preschool/daycare. The only men there was our minster and the principal, both of whom I knew very well and really didn't believe would ever abuse a child.
Do you have to take it serious if a 3 and a half year old says "daddy hurts me" to her mom?
So when we went to school the next day, I took the teacher aside for a few minutes and told her what my son had said. She was both taken aback and concerned and told me she would keep an eye on my son and see if she could learn anything further.
When I came to pick him up, she had a big smile. She took me aside and told me that the “man” was one of the eighth graders who happened to go in the bathroom when my son was there. Seeing my son struggling a bit with his overalls, he came over to help. Since my son was outside the stall, he thought he couldn't get them down, thus a few seconds of confusion occurred with this kind student trying to help my son pull his pants down while my son was trying to get them up and buckled.
Never ignore those kinds of statements but never make assumptions either!