Derrick Lewis is a VERY happy man after getting the W at UFC Fight Night in Austin -- 'cause he won ... but mostly 'cause his wife says she's ending his booty ban!!
The bad news -- we talked to Derrick and April the day after the fight ... and they told us he's too injured to get it on.
"The ban is over. I've been trying to get him all day, but he's tired," April told TMZ Sports.
"I don't got it in me, man -- I'm hurtin' ... I can't put in a half-assed performance, lay there like a starfish," Derrick added.
Lewis ain't lying -- showing us a serious injury he sustained early on vs. Marcin Tybura. It looks bad.
But, the Black Beast says he wants another fight soon ... and he's callin' out the scariest dude in the heavyweight division!