Tickling & Inappropriate Touching in Preschoolers
First of all, it is important for you to realize that neither you nor your son did anything wrong. It is wonderful to express emotions such as love and affection, and playful interaction is an important part of developing social and emotional skills. There is a difference, however, between what might be acceptable at home versus school, and what one person finds fun and another person finds invasive.
You shouldn't expect your preschooler to differentiate each and every situation, but you can share a general rule of thumb: simply ask people if it's OK with them to hug, tickle or touch. If this sounds overly simplistic, you'll be amazed at the difference it makes when your preschooler asks a peer, "Want a hug?" He may get responses ranging from a hearty "Yes!" to an annoyed "I need some space." Whatever the response, the direct approach gives your son feedback that will help him recognize and respond to social cues.
At this age, preschoolers are beginning to recognize the difference between boys and girls and parts of our bodies that are private. This is important as caregivers try to explain about "safe touching" and who can touch whom in "the bathing suit area."
Although preschoolers do not necessarily understand the difference between innocent touches and sexual touches, they are able to learn to read others' social cues. You can continue to play with your son at home as you have in the past, perhaps gently redirecting his hands if he gets overly exuberant. The play experience and bonding with you are most important to your child, not the exact location of his hands.