Hi Izy, when I was looking at your pic, my DH looked over and said, "Wow, thats an interesting looking quilt, I really like that "loose looking flower". :D Just between you and me, thats quite a compliment since he is such a perfectionist :D
I'm not sure about your corner, but a guess would be that you may have sewed a little farther towards the corner than you should have before you stopped and folded your fabric up, then back down to head down the next side of the quilt when you attached the binding to the quilt. I'm not sure I explained that so you could understand it...and I'm not sure thats it, :D but its my "best" guess, so I'll stick to it. The quilt is beautiful though and no one will really notice it but you...so don't worry!