Hello, I Am A Very Healthy 56 Year Old Woman

Hello, I am a very healthy 56 year old woman (albeit had treatment (surgery & radiation), for breast cancer five years ago (right hand side). Just noticed today a very light blue line encircling my lower arm (right hand side), approx. 3 inches up from wrist. While I am light skinned and can always see the veins in both of my arms, never saw this before (odd). Anything to be concerned about?