The United star, 37, appeared to slap the hand of Jacob Harding after he stormed off the field at Goodison Park following United’s 1-0 defeat, damaging his phone.
Ronaldo apologised to the 14-year-old afterwards but was interviewed by police under caution in relation to alleged assault and criminal damage.
In a statement on Wednesday Merseyside Police said: ‘We can confirm that a 37-year-old man voluntarily attended and was interviewed under caution in relation to an allegation of assault and criminal damage.
‘The allegation relates to an incident following the Everton v Manchester United football match at Goodison Park on Saturday 9 April.
‘The matter has been dealt with by way of conditional caution. The matter has now concluded.’
It is understood Ronaldo has agreed to pay compensation to the schoolboy.
Sarah Kelly claimed son Jacob Harding’s first trip to watch Everton back in April was ‘ruined’ by the alleged altercation which happened as United left the pitch after the match.
Miss Kelly, from Upton, Merseyside, said her 14-year-old son was left with a ‘bruised’ hand after the phone was knocked from his grasp by Ronaldo, as the boy tried to film the United star’s leg wound suffered during the match.
She said: ‘We were right by the tunnel where they came walking past — my son was there videoing them all. And then he lowered his phone because Ronaldo had pulled down his sock and his leg was bleeding.
‘He lowered his phone to see what it was — he didn’t even speak. Ronaldo then just walked past, with a terrible, terrible temper and smashed the phone out of my son’s hand and carried on walking.’
Miss Kelly took pictures of what she said was Jacob’s bruised hand and smashed phone screen.
The 36-year-old added: ‘You can see by the bruise that he’s made contact. I was crying, I was shook up, Jacob was in complete shock — he’s autistic and he’s got dyspraxia as well, so he didn’t really digest what was happening until we got home. He’s really upset and it’s completely put him off going to the game again.
‘Ronaldo’s a big player. My son’s always been like “Ronaldo’s going to be there” — he’s an icon. I’d understand if Jacob was waving it in his face but he wasn’t near his face, it was down by the floor checking his injury.
‘He’s an autistic boy and he’s been assaulted by a football player, that’s how I see it as a mum.’
Ronaldo posted an apology to his Instagram page after the game.
‘It’s never easy to deal with emotions in difficult moments such as the one we are facing,’ he wrote.
‘Nevertheless, we always have to be respectful, patient and set the example for all the youngsters who love the beautiful game.
‘I would like to apologise for my outburst and, if possible, I would like to invite this supporter to watch a game at Old Trafford as a sign of fair play and sportsmanship.’