Hi, I've Been On On The IUD Mirena For About

Hi, I've been on on the IUD Mirena for about two years now. I had it put in after I had my daughter. I had problems with breast tenderness & cramping in the past which went away very quickly after insertion. Today while changing I noticed my nipple was erected and extremely enlarged. I am sexually active and I'm kind of freaking out. With my daughter, enlarged nipples were my first sign of pregnancy. Should I be worried?