Hello and welcome,
This sounds like an endometrioma
. This is abnormal uterine lining growing in the scar tissue and is not very rare. However it occurs less frequently after cesarean as compared to other uterine surgeries.
Other possibilities are a lipoma
of the fat, or even a keloid excessive scar].
Get it checked by a doctor and get it removed if needed.
Hope this satisfies your query.
Thanks for using HCM.
Feel free to ask any more questions that you may have.
Dr Madhuri Bagde
Consultant Obstetrician and Gynecologist