3:39 PM PT -- Young tells TMZ Sports he's willing to fight whoever steps in the ring with him on Saturday ... including fellow ex-NBA baller Nate Robinson, who he said could use a reason to distance himself from the memes after getting knocked out by Jake Paul.
12:53 PM PT -- Young is speaking out on the bad news ... and since he won't be able to swing at Blueface in the ring, he's unloading one last verbal jab.
"He too busy getting his ass whoop (sic) outside the ring so who wanna take his place?" Young said on IG.
Blueface will not be stepping into the ring with Nick Young on Saturday -- the rapper has not yet been approved for a boxing license ... and now event promoter Austin McBroom is scrambling to find a replacement with only 3 days until fight night.
TMZ Sports is told the 25-year-old Thotiana rapper received a letter from the California State Athletic Commission on Tuesday informing him his application for a pro boxing license in the state would not be granted until he appeared before the organization in October.
Obviously, that means Blueface can't fight Swaggy P on Saturday's Social Gloves 2 card at Banc of California Stadium in L.A.