Vanes Martirosyan -- a stud boxer who just fought Gennady Golovkin last year -- was arrested earlier this month and cops suspect he headbutted his wife. TMZ Sports has learned 33-year-old Martirosyan -- a middleweight with a career record of 36-4 -- got into an argument with his wife in their Glendale-area home on Sept. 15. Our law enforcement sources say the altercation started as a verbal fight ... but then things took a violent turn. We're told the 5-foot-11, 175-pound boxer allegedly grabbed his wife by the arm and is believed to have headbutted her square in the face. We're told she was able to flee the home ... and after cops showed up to the scene, they found her with a bruise on her arm and a messed-up nose. Our sources say she declined medical aid ... but a police report was taken, and Martirosyan was arrested the next morning. He was booked for felony domestic violence. Bond was set at $50k ... and Vanes was released later that day.