The 21-year-old was introduced at half-time in the third round replay with the Hornets trailing and bagged an equaliser that forced the game to go beyond 90 minutes. Tranmere eventually won via an extra-time strike from Paul Mullin.
"I'm over the moon, it's a proud moment for me," he said.
"I'm not too happy about the result, but it's a learning curve for us. There was a lot of young players playing today and I think we'll go back, reflect on it and learn from it.
"They're [Man United] the team I supported when I was younger, so I'm disappointed, but it's an experience for me and all the other younger boys who played out there today."