My infant son has a swollen area on his pelvis that wasn't there a few hours ago?

Could be a hernia. If your baby is not in severe pain, you can contact your doctor's office to schedule a routine appointment to have it checked out. If your son is having pain, vomiting or any other worrisome symptoms, it's best to be seen right away. Hernias may present as a bulge in the groin and that condition can be diagnosed by a physical exam. Sometimes the bulging comes and goes, but best to call your doctor.