Is it a CL cyst and it just looks like a black hole? If so, this is very normal and a good sign, it indicates the ovary you ovulated from to conceive your baby. It kind of takes the place of the placenta till around 12 weeks, helping sustain your pregnancy.

I have a cyst on my left ovary which was actually ruptured before I knew I was pregnant. This 'cyst' is actually more a tumor, they thought perhaps a brenner tumor (alhtough I doubt it as they are exceptionally rare in pregnancy) but hopefully an endometrioma, because it's solid and very round. This looks very different to a CL cyst on a scan. Even in my case, with the abnormal cyst/tumor, they still just are waiting till the pregnancy is over to check it and whilst it's only causing my mild discomfort it's not a concern at the moment..