Hi, I’m making a scarf and ran into a hitch, which I am hoping is easily fixed.
I was knitting the first stitch on a new row when the new yarn I’d just tied on broke and I completely undid that first stitch. Now I’m short a stitch, and I have no idea what to do. Can anyone help me> :?:
Can you un-knit the last row? That way you can pick up that stitch you dropped and you can join the new yarn at the beginning of a row.
At least… I think that will fix the problem you described, unless I misunderstood.
Check out Amy’s “Fixing mistakes” videos – they may be able to help you out too.
I think I may be flipping my lid. I thought sure I replied to this last night, but now I don’t see my reply. :??
Anyhoo, at the risk of sounding like a total imbecile, how, exactly, does one “unknit” a row? 
Think of it as working backwards, from right needle to left needle.
First you insert the left needle into the stitch that your working yarn comes out of. Once the stitch is secure on your left needle, slide the first stitch off of the right needle. TADA!! You’ve just unknit one stitch. 
Thank you, ekgheiy! That sounds simple enough for even me.