UFC's Nick Diaz -- Feelin' Cheeky In Vegas ... With Hot Bikini Lady

Here's proof Conor McGregor wasn't the only UFC star who won in Vegas this weekend ... check out fellow MMA head-basher Nick Diaz posing with a trophy of his own.

Nick was in Vegas this past weekend for the big fight and hit up Wet Republic at the MGM Grand where he seemed to have both hands full ... with a super hot chick.

Turns out the woman in the bikini is named Heather -- and she's been close with Diaz for a while now.