What Do Nodules In Breasts Indicate?

Hi! I just had the result of my ultrasound of my breasts it says solid nodules, both breasts with probable benign features my doctor gave me 2 options one is to observe for 4 mos. or have a biopsy. I took the first option since I'm only 22 I'm scared to undergo operation. Is this safe to wait 4 mos. ? Or should i take biopsy? He didn't gave me medication to lower me from cancer risk.