Following Monday’s loss, Nuno said Mason was “not good enough” to officiate at the top level, leading to the Football Association asking him to explain his comments.
“I won’t apologise for my words and thoughts,” Nuno said on Wednesday.
However, he told a news conference he regretted “the timing” of them. Nuno, whose side host Tottenham in the Premier League on Sunday, added: “They were not in the best moment to come across because it could be a bad interpretation.
“I never question the integrity of a referee. What I said was about the ability of the referee.”
The FA will decide whether to act once it has received Nuno’s observations, which the Wolves boss says he will submit on 29 December.
Under current FA regulations, post-match comments that criticise the performance or competence of a match official are permitted unless they imply bias, attack the official’s integrity, are personally offensive, are prolonged, or are particularly unreasonable.
Monday’s game was the second time Mason had officiated Wolves this season.
“I never spoke about referees and I probably won’t do it again,” added Nuno.
“But I will not be comfortable if I did not say it because we want to go into a match not worrying about the referee from that game.
“Every time [he has refereed us] unfortunately we have had problems. We don’t want a repeat.”
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