I think once you turn the border around so the triangles are the other way it will feel right with the square in the corner. Your quilt is beautiful. Great job so far.

I don't know. To me it looks as if all the triangles are going in the correct direction. The problem I see is that the border on the left is short of what it should be. When you add a square in the corner, it should visually be "one" with the last print triangle on each side. Your left border is so short, the square would not connect both triangles. (Actually, I see now that the top border is also short of where it should be.)