don't be too worried about it. Shedding can cause a snake to do this, so can the smell of food, and stress. Just don't pull away or drop the snake when he is she does this as it will show the snake that you will leave him alone if he strikes at you. besides, the bites don't hurt much at all.
If you have only had the corn for 4 days, then you are already handling it way too much. You need to let it settle in for at least a week before handling it. That means the only contact the snake has with you that week is you cleaning the water bowl.