The former Scotland forward scored on his Australia debut against New Zealand in order to get into the World Cup finals.
He came on as a substitute and scored a penalty in a 2-0 win.
Although he was capped twice for Scotland, he was able to switch to Australia because his mother is there.
He said after his first 30 minutes that he was buzzing.
After his shot was blocked by a New Zealand hand, he won the penalty.
He told Channel 10 that he was just getting on. The boys have been different class and I was just wanting to get on the pitch, so I got a good 30 minutes and the ball fell to me and I caught it, but the boy hand balled it and I was angry.
I thought I had to take the pen and finish my dinner after the referee gave it to me. They asked me if I wanted to take it, and I said yes, it's a goal scorer's dream.
A group of players were allowed to return to their clubs after Thursday's win over the same opponents as head coach Graham Arnold chose a completely changed starting XI.
Three of the six players who made their international debut were on the bench.
After Mitchell Duke's opener, it was 18-year-old debutant Garang Kuol who set up the club's second goal, which came from the penalty spot.
It was three years after Arnold first said he wanted him in his squad that Cummings made his debut.
It's everyone's dream to make the World Cup squad, and it's my dream as well.
"All I have to do is go back and work hard, score goals, and you never know," he said.