"I've got a massive 'tatie in my sock"
According to the Imperial War Museum's "Make and Spend" website, the term "potato in your sock" refers to a sock that needs to be mended. The origin of the phrase is the process of repairing a sock hole by darning, which the use of a round object, such as a pototo or a specialized darning egg, to stretch the whole over the object so that the person repairing the sock finds it easier see what they are doing.
I don't know how to darn. It's a good job I got some new socks for Christmas.
I've always thought novelty socks are for losers; unfortunately, I got a box full. Mr Benn socks! I might be a loser wearing them, but I am a sucker for nostalgia, and they came in a great box.