New knitter needs help

I cast on starting with a row of knit, I complete my next row and have this big loop, what am I doing wrong?

This is actually kind of normal. You’ll find that the last stitch on a row is typically abnormally loose. It will equal out as you continue to knit. Be very careful with that stitch however, as it is very easy to pull the working yarn incorrectly and accidentally knit into the wrong portion of this stitch. It’s also very easy to pull this and think that there are two stitches there when really there is only one. This is one of the areas where new knitters accidentally add stitches.