Pompey belied their League One problems during a fine start, only for the Premier League quality of Ralph Hasenhuttl's side to tell as the visitors romped to a 4-0 Carabao Cup victory.
"It means the world to the fans," the forward said. "To me being from Southampton, it's a huge moment.
"It was massive. We knew this was going to be an occasion, we knew it was going to be tough coming here with the atmosphere and how well supported Pompey are."
Asked if scoring against Pompey was something he had dreamed of, Ings said: "It's a crazy feeling. It really is.
"I've been very fortunate to play in big derbies, but for me personally this one tops it.
"When the draw was made, I just couldn't wait for the fixture and when I got the nod to play I was just so excited to step over the white line and do my best for the club."