What you need to do is put the sock on the other way round so the holes are at the top of your foot and not underneath. I do remember how to darn socks, but if you darn a hole underneath the heel they are never as comfortable, and they soon wear out again.
The next step is to fold over the excess sock so the hole cannot be seen. You could actually put some stitches in to hold it permanently in place, but I can't be bothered.
Then when you put your boot on and lace it up, all the tattyness is hidden inside, and it is just as comfy again. I reckon you could double the life of your socks if you do this, thus saving a lot of money.
I have just eaten my lunch, two crumpets, and scrambled eggs on a bed of raw spinach. Luverly jubberly. Some fresh strawberries for after, which I found in my front porch. I have a strong suspicion that they were left there by my friends Janet and Paul. Thank you, they are so sweet. The strawberries are as well ;o)