Is Presence Of Hemorrhagic Cyst Dangerous?

HI,Im 35 years old, 1.71cm, 56kg. I had a miscarriage at 10 weeks, its been a month, i've only been clear of all tissue from the miscarriage today and as i had a scan they told me i have a 35mmx40mmx21mm haemorrahgic cyst on my left ovary. I had a scan 2 weeks previous and it wasnt there. They're giving me a follow up scan in 3 weeks time. I'm worried that 3 weeks is too long and that the cyst is too big. thanks, Maria