I posted an answer to your question in the Welcome to the Forum section, where you asked what can you do now? Here is a copy/paste of what I answered, and this will complement Ingrid's helpful post, as well:
Hi Lisa! :waving:
Is the bind-off edge at the end of a scarf? If so, here is what I would do: rip out the bind-off row, and the last full row that you knit...and bind-off on that row. This will give you the extra yarn you need!
If the bind-off edge that you are currently working on will be hidden in a seam, why not tie a similar weight yarn onto the end of your current working yarn, and continue binding off as usual? If your yarn is wool, you could use the "felted join" to join the 'fill in' yarn to the current yarn. There is always the "Russian join" for non-wool, not-feltable yarn. Both "joining" techniques have video clips here at KH. Go up to the VIEW VIDEOS tab at the top of this page, and select TIPS. Amy has two very nice videos for "felted join" and "russian join". And of course, you could always tie a nice neat knot, too, and trim off the excess yarn. I put a dab of Dritz "Fray Check" on the knot.