Well, first of all, it depends on your gender, since men and women have different things in their groin...
Is the pain aggravated by coughing or straining? Do you feel any bulge?
In this case, it may be an inguinal hernia, which is quite common in men.
You can read more here (
http://www.nlm.nih.gov/medlineplus/ency/article/0031...), and consulting a doctor may also be wise.