Conor McGregor might have to wait ... another huge fighter says he's gonna take a chunk out of Floyd Mayweather's ass if he returns, and this guy is a boxing superstar.
The guy is WBC super welterweight champ Jermell Charlo, who's fresh off a devastating first round knockout of Erickson Lubin a couple of weeks ago.
Charlo hit the Lakers game Thursday night with Brandon Watson -- co-owner of the Team Watson Boxing Gym in L.A. -- and told us if Floyd (who's been working out) is serious about a comeback, he's down.
For the record, Floyd and Charlo are pretty good buddies -- and Charlo respects Floyd immensely -- but wouldn't you fight your pal for a $100 million payday???