Hi there i just read your post and found this link,although yours is around the uterus,it contains same info hope it helps,congrat.
http://en.allexperts.com/q/ObGyn-Pregnancy-issues-1007/hematoma-uterus-1.htm
Its not something to be too seriously worried about. I had a hematoma during my pregnancy (however I was bleeding with mine since it was quite big). Its actually quite common to see one in early pregnancy. Its basically that when the baby implanted it ripped your uterine lining causing you to have bleeding behind the sac. They usually resolve on their own before the 20th week of pregnancy.