Mammoth sunflower with weird gash/stopped growing

So this Mammoth sunflower used to be the only thing growing in this patch, but some of its neighboring plants now kind of shadow it.

For the past 2 weeks it stopped growing/ started growing towards the side to avoid shade. It has also developed the pictured gash with some ants guarding it. Any clue what that gash is about? Will this plant still grow a flower or should I cull it where it stands?