Nelly is apologizing for a video of him receiving oral sex which, somehow, got posted on his social media -- and he says the old clip was never meant to see the light of day.
The "Hot In Herre" rapper started trending Tuesday on Twitter after his IG story briefly included an uncensored video of a woman performing oral sex. The video was quickly deleted, but not before folks were able to capture screen recordings and repost.
Nelly tells TMZ ... "I sincerely apologize to the young lady and her family, this is unwanted publicity for her/them. This was an old video that was private and never meant to go public."
As for how it ended up getting on his Instagram account?
Well, it sounds like Nelly may have been hacked, because his team tells us they're investigating a breach and are concerned more of Nelly's private content may also end up online ... including financial information, personal documents and passwords.