It's all spelled out in a police report, obtained by KTNV, in which cops say they were called to the Cosmopolitan on July 3 to investigate claims that Kalabrya Gondrezick-Haskins had attacked the NFL player in their hotel room.

In the report, cops say Dwayne told them the fight went down because his wife was disgruntled after he had gone to a nightclub with friends without waiting for her and the rest of the group.

Cops say Dwayne had a busted lip that needed stitches, as well as a missing tooth. They described the injuries as "substantial in nature."

Cops also say in the report that the 24-year-old QB "would most certainly require dental work to repair his teeth."

In the report, cops say Kalabrya told them she was not sure how the football player suffered the injuries.

Kalabrya was eventually arrested ... and court records show she's been since hit with a felony charge of battery which constitutes domestic violence with substantial bodily harm.

Records show she's due in court next month for a hearing in the case.

As for the couple's relationship, it's clearly a confusing matter ... 'cause just over the weekend, the two had posted what appeared to be an engagement announcement.

In their social media posts ... the quarterback and Kalabrya showed a video of Dwayne getting down on one knee at a Vegas restaurant and giving Kalabrya a massive ring.

But, in the police report, cops say the couple told them they had actually already gotten married in March after dating for over a year.

Cops say the two also told them they were in Vegas with friends and family this month to "celebrate their commitment to each other."