The 18-year-old defender has yet to feature for Fulham's first team but earned a call-up for the national side's tour of South America on the back of some standout performances for the Under-21s.
Having sat out the 1-0 defeat in Uruguay, Donnelly was awarded a first cap as a late substitute in Wednesday's 2-0 loss to Chile and is already eager for more.
But with Northern Ireland well stocked in defence - Gareth McAuley, Jonny Evans, Craig Cathcart and Alex Bruce were all absent from the trip - he knows he will need to make an impression on the Cottagers first team.
"I'm very proud to get on and make my debut, especially against a country like Chile who go to the Word Cup with a lot of hope," Donnelly said.
"With 10 minutes to go I could see a few of the boys warming up and I was getting a bit edgy, not knowing if I was going to get on or not, I think I was kind of giving (head coach) Michael (O'Neill) the eyes, trying to get his attention, but I was just happy I was able to get on in the end. It was brilliant.
"I hope I've done enough in training to make Michael keep an eye on me. I think I've done well and hopefully he will consider me for the next trip, whether it's a friendly or one of the qualifying games.
"The big plan for me now is to push on and try to get into the first-team at Fulham next season. If I do that, I can make a bigger claim to be a regular in the Northern Ireland squad."