I’m a newer knitter and this is the first time I’ve had to face this. There’s a knot in my yarn, and I’m in the midlde of a row. It seems the yarn must’ve snapped and the manufacturer just tied it together. It’s definitely been cut and the tied.
I’m in the middle of a 200 stitch wide row!
Do I just knit the knot in to the row, or cut it and then somehow get new yarn in there??? I don’t know what to do!!
Please help!
Ouch! That’s a very large row. Unfortunately, the best thing to do is to undo what you’ve done in this row, cut the yarn and cut out the knot, and then start the row over and join the yarn again. You could keep knitting, but then you run the risk of the knot coming undone and your beautiful piece unraveling, which of course you don’t want. lol.
In the long run, it will be better to fix it now than have to fix it later. Good luck! 
I would add that as long as you have frogged the row you are working on to the beginning, I would cut the yarn there and tie the ends together at the beginning of the row. That way you won’t have a knot to contend with in your work and you can weave in the two ends at the beginning.
What fiber is the yarn made from? If it is wool, you can felt it together. I did this in the middle of a row and it only shows a little on the back. It really depends what you’re knitting and how much you care though.
You can try the felted join or the Russian join. Or you can leave ends hanging and weave them in later like normal - yes even though you are not at the start of the row! This is what many people do when they knit in the round, there are no edges to hide ends in, and you can still keep them invisible. Get good at weaving in invisibly though - there is a good Knitty article on this!
You could also hold the wools together and knit a few stitches, check out Techknitter’s blog for more on this and general invisible joins.
DO A RUSSIAN JOIN!!!
Its my favorite. Google it. Its magic. It works for acrylics.
The felted join is just as good but only works for things that felt.
I hate weaving in ends and almost always knit hats, so these two methods are the reason I will change colors.