The Ghana international completed a season-long deal to Stade de la Beaujoire - Louis Fonteneau on Tuesday, having had limited opportunities at Estadio do Dragao since joining from Lorient.
He made just five league appearances involving one start for The Dragons, failing to find the back of the net.
"I arrived in Porto last January, I played two Champions League games and we won the league" Waris told reporters.
"I was a little embarrassed by injuries and I could not play the last matches of the season. But for me, the result is positive.
"I talked with the coach in the off-season and he wanted me to stay but I really wanted to play every game, so that's why I asked to go on loan.
"I think it was the best choice for me to come here to progress and play even more."
Waris' club woes have affected his place in Ghana's national team, having been out since July last year.
"For me, what matters are the results of the team [Nantes]," Waris said.
"I want us to finish as high as possible and achieve our goals together.
"Playing for the Ghana national team is always an honour.
"Playing with Nantes will give me that opportunity to play at the 2019 Africa Cup of Nations with Ghana."