Spraing is brown lines underneath skin, blight is brown areas under skin - yours look like something in between the two, so I would not rule out blight, but it could well be
Spraing. If you scrape a different potato, you may be able to identify it accurately.
Unfortunately, with most of these diseases, the damage is done by the time you discover it, but there is a great variation in weather conditions to cause these problems and different varieties are more susceptible than others.
