The Glasgow man was a second-half substitute in Scotland's Castle Lager international against Samoa in Durban.
But things went wrong when he tried to stop Alesana Tuilagi, but the big winger brushed aside the tackle and raced in for Samoa's third try in their 27-17 win.
In today's Evening Times Pete said:: "I'm absolutely gutted. I'm very proud to have represented my country at last, it's something I've been desperate to do since I started playing, but I'm really disappointed with the way it went.
"I missed a terrible tackle and that cost us the game. Alesana is a big guy, but I should have tried to go lower than I did. I was really disappointed to miss it.
"This week I'll be out on the training field practising hard. I'm going to get big guys like David Denton running at me. I'll make sure it doesn't happen again.
"So it was not the best start but I'm determined to keep my head up and make sure my next performance is a lot better.
"During the anthems, I was fighting back the tears to be honest. I was quite emotional.
"Then, during the game, I had to make sure I was keeping up with play. There was a lot happening, so I was just trying to stay in tune with the game so I knew what I wanted to do when I came on.
"Getting on the field was a great feeling. But you don't have too much time to think about that."