A lot of children do this kind of experimenting that can actually be identified as molestation. If you need help to get over this then you need actual professional help. Find a therapist and open up to them. At least give some consolation to yourself that you haven't hurt them physically, and it might even help if you talked to them if they are still in your life. See if they feel abused, if they remember it as negative experience or if they remember it at all.
Children start generation sexual thoughts as early as age 4. They try to experiment with it at very young age (not all of them). So what happened to you here is pretty common occurrence, don't beat up yourself too much about it, but also don't postpone seeing a therapist.