On a mammogram what does stable right breast nodule consistent with benign etiology (br-rads 2 benign) should i have had a biopsy dr wasn't concerned ?

Up to you: Means you have benign appearing ' breast nodule ' that did not change from previous mammography . Now you have an option of observing till next mammogram or get a image guided core needle biopsy , will have tissue to find exact nature of that nodule and will take away , your worry ( no tension between mammographies )

Routine screenin: ACR currently recommends routine screening for Birads 2. In practice it is used as a synonym classification for birads 1 for those wishing to make a minor distinction or trained not to use the word normal for legal concern that it is too broad a term.