In desprete need of scarf help

Hi everyone! I hope someone can help me!

My friend is a huge Harry Potter fan and wanted a Sytherian scarf. So for her bday I learned how to knit just to make this scarf. My friend at the dorms taught me, so when I came home for break I went to change from one color to another (tried looping the silver over the green and tried to knit it in without tying) and realized I needed another row. So I tried to put the stich back and you can guess what happend.

I messed up and undid the last stich on the needle and now its just a loop!

Can someone please help me! I need to figure out how to fix the stich or how to undo the whole row so I can reknit! My friend is completely unreachable and I dont know where else to turn!

If it’s just one stitch that’s become unknitted, put it on the needle by itself, in your left hand and knit it again.