Gently remove the binding and start over. But before starting to sew the binding on again, find out what happened that you stitch 1/2" seam instead of 1/4". We all make mistakes but the important thing is to have learn from our mistakes so we don't repeat them again.

Good for you for using the love/hate relationship with Mr. Ripper. You'll be glad you did.

My girlfriend deliberately sews her bindings like that. Then she rolls the extra on the edge so that her bindings end up very plump and full. I prefer sewing it on a bit smaller and having a flat edge. I don't know what she does in the corners.