Thanks for the query.
Usually 4 cms size simple cyst
may not lead to much problems.
Simple cyst with clear fluid and without septations etc can be managed by periodic followups.
For more details : http://srsree.blogspot.in/2013/11/ovarian-tumors-management-of-ovarian . html
As, you are getting pain, better to rule out possibilities like:
-Increasing size of the cyst, exerting pressure on surrounding structures.
- Twisted ovarian cyst
-Rarely rupture of cyst etc.
So, once consult gynecologist, get examined and go for ultrasound
along with doppler.
With these the possible cause for your problem can be identified and treated.