Powell was dismissed from the Wales squad following a breach of discipline in the aftermath of the last-gasp win over Scotland a fortnight ago.
The 28-year-old was charged by the Police after being found in possession of a golf buggy at a service station just off the M4 in the early hours of Sunday, February 14.
Powell is now concentrating on impressing for the Blues as the Magners League begins to reach its climax but he is aware that he may have burnt his bridges as far as international rugby is concerned.
"I regret terribly what I did. I know it could cost me my international career and that tears me up inside every time I think about it," said Powell, who started against both England and Scotland earlier this month.
"I have let Wales down, my family, the fans and everyone involved with rugby, especially Warren Gatland, who gave me the chance to play for my country.
"There is a danger that I won't get the chance to play for Wales again.
"It's going to be tough, but it's up to me to rebuild my career and get it back on track."
The only way Powell will be able to do that is if he first performs well for his region. The 2009 Lions tourist didn't feature in the stunning Magners League win at leaders Glasgow last week but he is likely to be a key figure if the Blues are to surge back into Play Off contention over the coming weeks.