The skin of your scalp can become dry and irritated just like the skin of your face. Use good quality moisturizing conditioners on it. It should recover in a week or two.
However, when you bleach your hair again, you run the risk of drying your scalp out again.
Was the bleach left on longer than usual?
Did you use a stronger product than usual?
If you bleach your hair regularly and this is the first time it has happened, you may have become sensitive to the bleach. If you think that is the case, consider alternative hair color methods - such as highlighting.