Nick Diaz has a message for Colby Covington -- stop talking, let's fight.
Colby just went off about Nick during an interview with Helen Yee -- claiming he had signed a a contract to fight Nick at Madison Square Garden in 2018 ... but Nick wouldn't put pen to paper.
"Nick was on board, he gave his verbal to the UFC that he wanted to fight me," Covington said ... "but when they sent him the contract, he never signed the contract.
"He added, "We find out that hes a Stockton soy boy.