Thank you for contacting JustAnswer.
I am sorry to hear about the problems you are experiencing with your son. My first question would be if this is a first time occurrence or if there has been a pattern of such behavior. If this is a pattern then I would be more concerned. However, if this is an isolated incident it is less of a problem. It would be helpful for either you or his father to calmly explain that certain information is for adults only and that this is in part because it can be confusing and overwhelming for children. You can invite him to ask either of you questions about anything that he does not understand and offer books that are appropriate for children to explain anything that he may be interested in. The more calm you remain the easier this will be for him. I would also suggest that you consider putting a password XXXXX the iPhone and block the computer to prevent this in the future. There are many options to give you controls for the internet. Placing the computer in a place where it is in view of other members of the family can help deter problems, as can keeping smart phones unavailable to children. If you feel that he stumbled on the site accidentally then a consequence may not be needed. However, if this seemed to be intentional then perhaps a week of no electronics could be reasonable.
Please let me know if I can help further.