The 26-year-old was out in Liverpool on Saturday night celebrating Magpies captain Jamaal Lascelles's 23rd birthday when, according to The Sun, one of the party "took exception to Gayle discussing his £35,000-a-week earnings".
The unnamed man in question then allegedly punched Gayle in the face twice, knocking him - as well as four of his teeth - out.
"The night had started fine, but the champagne was flowing and things got out of hand," a source told the newspaper.
"One lad took exception to Dwight talking about his pay and took a swing at him. It was a real shock. He hit him hard and, as Dwight went down, hit him again. He was out cold.
"Everyone was in shock. Dwight was texting people the next day saying he'd lost four teeth. He was really angry."
Merseyside Police confirmed that they had been called out to an incident at 4am on Sunday but said that the group had dispersed by the time they arrived.
Gayle, who joined Newcastle from Crystal Palace over the summer, is the Championship's top scorer with 11 goals in 16 games.