S tefon Diggs waited until the bye week to celebrate his birthday, but it was well worth it -- his lady, Cardi B , made it unforgettable by twerking and singing for his big bash!!

Cardi and mutual friends had a toast to the New England Patriots wide receiver's 32nd trip around the sun on Thursday in Miami ... days after his actual birthday (November 29th). Getty

While Diggs was enjoying dinner and about to blow out the candles on his cake, Cardi began singing Stevie Wonder 's "Happy Birthday" along with the friends in attendance.

That's when the real party started -- the "Outside" rapper began shaking her ass for Diggs at what appeared to be a nightclub ... and of course, he couldn't help but watch. Remember Cardi's steamy boat twerk sesh for Stefon?!

FYI, the song s

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