It might have stretched now after sewing and ripping. Why don't you put it on the cutting mat and trim of the seam line with all the glued part and toss that, then measure your quilt side and see exactly how long it is. Also make sure the corners are square with the other borders. You might want to check the other border and see if they measure what they should.
Whenever I rip something, I usually hold the steam iron over the place and give it a burst of steam and pat it down to the ironing board, to take out any fullness . Once it is flat you and then iron it and proceed to the next area.