I Am A Breast Cancer Survivor Since 1997....i Had A

I am a breast cancer survivor since 1997....i had a mastectomy right breast.....about 6 months ago I noticed my left nipple is inverted....i didn't worry about it because i am sure that when i had my mammo done at the end of May that it was inverted then & everything came out ok w/my results...should I be concerned.....