Its street slang from the US. You will hear it in all those US imports on Netflix. You will come across it on social media. Its only a matter of time before a politician getting down with the kids uses it. As an expression it's a way of admitting a mistake, and apologising for that mistake, without actually apologising. Someone who uses it is really saying,
"I did something bad, and I recognise that I did something bad, but there is nothing that can be done for it now, and there is technically no reason to apologise for that error, so let's just assume that I won't do it again, get over it, and move on with our lives."
We have all heard apologies that weren't really apologies now we have an expression to cover it.
Blair McPherson www.blairmcpherson.co.uk