I had quite bad veins on the back of my legs during pregnancy. I also had a C-section birth. I just noticed while in the shower that I have a lump on my back of my leg in the bend where your knee is, which is bigger than a pea. And it's blue?
Hi, it sounds like a varicose vain, which are super common. However due to having C-section you need to be wary of deep vein thrombosis (blood clots) so if you get hot points in your leg, any swelling or pain of it or any chest pain, you need to see medical advice ASAP.
I would recommend you get it checked out by your family doctor or health visitor. Do you know how long it's been there, is it getting bigger, is it painful?