My 10 year old son is composing of pain in lower abdomen area when he caughs. Could be hurnea?

Possibly. An inguinal hernia usually presents with a visible or palpable bulge. Pain alone without a bulge is more likely to be from another source, such as a muscle strain. He should be examined by a pediatric surgeon.
Possibly. Occasionally, hernias in children can cause abdominal pain, however this is uncommon.
Maybe. Certainlt is possible. No way to tell without a good exam. Call your doc and get an appointment to haveit checked out.
Possibly. Ask him where it hurts. Have him point out the area and demonstrate with a few coughs. If you see a bulge at the navel or the navel is tender then he has an umbilical hernia. If you see a bulge above his scrotum the he has an inguinal hernia. Have his pediatrician take a look.
Appendix. This could be appendicitis - this pain usually is felt in the lower abdomen or on the other side in some people. Have this checked out at your doctors.