Floyd Mayweather Now Best Friends With Larry Merchant

You'll remember ... Merchant and Mayweather really got into it during their post-fight interview last September ... when Merchant famously screamed, "I wish I was 50 years younger and I'd kick your a**."

But Sunday afternoon in Los Angeles, Merchant said he and Floyd buried the hatchet over the weekend in Las Vegas and each apologized for what went down.

As for Justin Bieber's appearance at the Mayweather-Cotto fight ... Merchant said he was "trying to get some face time on television. I think he needs it badly."