Am 27 yr old. I did ultrasound of pelvis. Ovary reveals haemorrhagic cyst 2.4 cm? What's next?

Not sure anything. Hemorrhagic cyst is likely a corpus luteum. Often hemorrhagic and of no real consequence. Essentially every month the follicle grows and ruptures, bleeds some (sometimes more than others) and becomes a corpus luteum. The cl produces mostly Progesterone to ready the endometrium for implantation.