Don't worry, this is a mistake that many of us make -- if I am cutting and let my mind wander the least little bit I am guaranteed to have miss-cut at least one block (or a whole border length -- which is really annoying). As others have said, if you have a scrap that is at least 1 1/2" wide, sew it on and then re-cut the block. When I patch like this, I try to check the adjacent blocks and make sure the seam does not encounter the seams of any adjacent block. I also sometimes press the seam open so I have less bulk, but once quilted only you know it was a mistake.