The Royal attended the WellChild Awards in London yesterday (3rd September) as he is a patron for the charity, which helps terminally and critically ill children in the UK.
Before coming face-to-face with Harry, six-year old Alex Logan had previously told ITV News that when he met the Prince, he would say: "I'm glad you've got your clothes on Prince Harry!"
The 27-year old soon caught wind of Alex's remarks, wagging his index finger at the boy and joking: "You keep looking up at your mum. It looks like you're dying to say something but you're worried she'll tell you off.
"I heard you were on ITV earlier and you said something cheeky but let's not talk about that here."
According to Digital Spy, sources claimed that Harry was worried his naughty antics in Sin City would 'overshadow the charitable cause.'
Earlier this week, reports suggested that the Royal was "furious" with claims made by Las Vegas party girl Carrie Reichert that she had joined him for the infamous game of strip billiards, revealing she also shared a kiss with Harry.
He is said to have denied her allegations, with a Palace source telling The Mirror: "Harry is furious about these claims and wants it to be known that they are false. He says this girl was not there on the night of the party.
"The Palace have been braced for claims like this. It's no surprise that people will come forward and say they were in Harry's suite, but he insists that this girl was not there that night."