That happened to me when I was a collage student. The officer only need to say the words "I smell pot". I knew he didn't, he knew he didn't, but those words gave him reasonable cause to search my car and belongings. His fishing expedition was quite unsuccessful and legally violated the Constitution.
If the officer wasn't lying, then there was no violation of the Constitution. The Constitution doesn't explicitly speak to the issue of police lying. Your complaint, if you have any, concerns police corruption, not violations of the Constitution.