Cody McDonald sealed a 1-0 win after the half-hour but Hughes felt the Sky Blues marksman committed a foul in the build-up.
It was City's first home win since January and they have now taken seven points from Pressley's three games in charge.
He said: "I have seen the replay three times and there was no foul.
"Cody used his body really well and turned the opponent and then a terrific finish for him.
"I am delighted for him because his work ethic for the team was terrific. Goals give strikers confidence so I am really pleased for him.
"He's a very intelligent striker, he moves well across the line and likes to dart in-between people and that was the movement for the goal."
"We hadn't won at home for two months so winning at home was a real monkey to get off our backs but for me the most pleasing thing is that there is a real resilience and determination in the group and I don't think they gave up a real chance in the entire 90 minutes.
"We have given ourselves a chance of getting into those play-off places."