First off can I say this forum looks great and hope I can contribute a bit in the future but today I need some help

I have some Maris Pipers and King Edwards planted in my garden and the few flowers that were on them have died so though I would have a look and see if there were any big enough to eat (probably bit early for these varieties??) anyhow there were a few but when I washed them I found there were quite a few brown spots/crack type spots on the surface of the potato what is it?? and is it a major problem??
Thanks for your help