Kissing Penis's

I was getting my son ready for daycare the other day, and found him in the bathroom staring in the mirror.  When I went up to him and asked him what he was doing, he said, 'Mommy I am sorry for kissing ****'s penis.  The person that he is talking about is another 4 year old at his preschool'.  I let him know that it is wrong for him to do this and that his penis is private.  When he left for preschool today, I let him know that if it happens again, to tell the boy and tell his teacher, and that this is not allowed.    (He is saying that they both did it to eachother, but that the other boy asked him first).  Not really too sure where to go with this.  The other boy and my son do not get along the majority of the time, they both vie for another boys play time. Do I speak with daycare or the other kids parents?  I don't want to overeact and cause embarrasment for him and create a problem that might be normal.  My boy is a curious one, I have found him 'playing doctor' as well as showing other boys his penis, but this seems a bit more.  Any adivse is appreciated. . .

[margypops]

It is possible it would happen again so I dont think you are over reacting if you speak to the teacher as it happened at school, by the way is no one supervising there ?

[AnnieBrooke]

Did he say it as though it was done as a dare or harassment, or did you think this was done for the sexual aspect (as much as a small child can understand sexuality)?