There are a few theories as to what causes this pain;
Irritation caused by blood and fluid when the egg is released. The blood and fluid can irritate tissues in the abdominal lining.Bruising is caused during ovulation when the ovarian wall ruptures.Fallopian tube muscle contractions cause discomfort. The contractions gently move the egg towards the uterus.
If you experience cramping after ovulation, it is possible that you are feeling the effects of implantation.