[mark.carline]

See this picture:

[DD.]

Looks like common scab. Potato is OK to eat.

Can be caused by alkaline soil.

[Salmo]

Agree with DD. It is common scab. As well as alkaline soil it is encouraged by drying out just when the tubers are setting. Add plenty of organic matter to the soil. Some varieties are more prone to scab than others.

[mark.carline]

ok thanks!!