You need to zoom way out and take another pic. It looks like that horizontal piece isn't nailed to or even touching the stud. Is that fire blocking? What's the metal and paper?
I would not worry about it too much. It?s not a crack it?s a knot in the lumber. It looks like a Simpson strong wall (the metal thing) right next to it, plus there?s another stud tied into the one with the knot. Btw a zoomed out picture would help.
