Hematoma

I went in for my first vaginal ultrasound being 7w6d. The baby's heart rate was 162 BPM. & doctor told me "it must be the season for hematomas." I have one that's 1 cm long behind the baby.. should I be worried? He never recommended anything like bed rest, no sex, nothing.. he said it should either bleed out or reabsorb.. I am so scared. First pregnancy & I'm only 20. Don't wanna lose my baby..