Bob Arum to Photog -- 'Sorry' I Said Bet On Manny ... Here's Your $100 Back

Bob Arum just put his money where his mouth was -- giving a paparazzo (not ours) a $100 ... to apologize for telling the guy to bet on Manny Pacquiao!!!

Manny's promoter was leaving Craig's in West Hollywood this weekend ... when the photog approached him and reminded him that he told bettors to put their money on PacMan to beat Mayweather.

Obviously, Pacquiao didn't win ... and Bob felt bad ... so he reached into his pocket and PERSONALLY paid the guy back!!!