Chris....... what yer done?
If you can't tell us here my suggestion is GET RID of yer GUILT by going down the local police station & confessing (if it was a physical offence).
If it's an internet offence involving downloading images ect., juz delete the files concerned, wipe the free-space & don't do it again. It's a criminal offence to download such stuff, but the police are far more interested in real crime rather than someone looking at random pixels on a screen which when joined together in a certain way make an image which is recognizable as a human-being. YES....... downloading this sorta thing is a criminal offence, but not up there at the top of the ARREST list. Real crime is about wrecking kids lifes by taking sexual pictures of them, or adults doing sexual stuff with them. Though the kid might like it at the time & even initiate the contact, in later life they'll 99% likely hate yer for it, hate themselves & resort to using a razor blade to cut-up their arms, legs, ect. in an attempt to relieve the contamination they feel.

If it is the former then for ta boys sake yer REALLKY need to be a man & go to the local police station & explain what yer did with the boy.
If yer don't, then though he might have liked whatever yer did at the time I CAN GUARANTEE that when he's an adult & looks back he'll see it as contamination. He could 3 things: Nothing, resort to self-harm (with razor blades, alcohol, drugs), or report you too the police.

Surely it's best to go yerself if yer did anything sexual with a minor (under 16 in UK).

God's looking down on yer, & if yer don't do ta right thing Big Brother will be breathing down yer neck too.

Kristian