How big is it and more important is the sides smooth and in the same plane or is it jagged and offset in elevation one side to the other.
Must be one of them crap new houses with concrete that ALWAYS CRACKS
(just like all concrete always does, chuckle
, where did they dream up that theory??????????????)
You can fill it with any cement product. I always like thinset for that type of thing, it will bond better than just about anything commonly available.
Your danger is the "CRACKING
" is not over. Like bad news those crap houses just spread, faster and faster over time.
Might put the vinyl down so it is easy to rip back out and replace if the "A For Mentioned Crack continues to go wild". The vinyl should tolerate minor cracking for a bit of time.
Couple of pixs are worth a zillion words.