I typically use a story board to tell me where my pieces will fall before ever starting the job. Since it sounds like you already laid the floor, just cut a 1 inch piece to fill that gap. Don't forget to leave room for expansion.
Hey, sometimes there can be twenty walls...ok maybe not twenty but several walls and one my need a 1 ich fill just so you can make the other open or main areas look best and uniform. Thats the way it is. Just fill it and throw on the base or trim.
in a perfect world--which this is not---- you would have measured and compensated for this by cutting down the first row giving you two equal sides---since that ship has sailed just cut to fit and astound small children with your hard won wisdom---if you do this a second time dont tell a soul---you know how people get