My guess is that you started knitting backwards the second day. When you picked up the needles, the hat turned inside out, so you began knitting on what had previously been the purl-side/inside. To confirm this, look back and see if you find a hole. At the point you started knitting on the wrong side there will be a noticeable hold between the stitches where the turn was made.
No real reason to rip it out. If you like the textured stripe you have created leave it. If you want to go back to go back to your regular stitch you can do that at least two different ways.
1) you did not say if you know how to purl or not. If you do, we can consider that your hat is being knit 'inside out' now. Switch to purl for the rest of your hat, doing decreases as P2Tog. when you are done flip it inside out, and voila.
2) You can turn the hat inside out again, and start knitting. To avoid the hole this time, before you turn the hat inside out, bring the yarn forward, slip one stitch from the left needle to the right, bring the yarn to the back, and slide the stitch from the right needle back onto the left. Now turn hat inside out and begin knitting.