Hi Julia F, welcome to the forum. I have found the information and support invaluable in the past year.
As for your itchy boob. I have what sounds like the same kind of itch, but on my right upper arm.
It's been driving me nuts for some weeks. Originally there was nothing to see and the itch was inside, scratching did nothing to help. It eventually went a bit bumpy and is now subsiding.
I remember this happening about 1 1/2 years ago, it went away on it's own. I really think it could be hormonal as when I was pregnant with my son I had the same internal itch all over for months. Stopped pretty much when he was born.
Still best to get it check out for your own peace of mind👍