✔ 最佳答案
I guess you are lucky if you haven't had sore lymph nodes or breast cysts before now. Neither one is dangerous or rare. I wouldn't be at all surprised if covid shot would provoke a sore lymph node; this is just a sign that the lymph node is working harder than usual. And so I'm guessing that is what it is, rather than a cyst.
Breast cancer typically will not move, and practically never happens at your age.