If your 4-year-old child is complaining of lower abdominal pain, it is important to monitor their symptoms closely. If they start experiencing other symptoms like diarrhea or constipation, or if the pain persists or worsens, it may be a good idea to consult a doctor. In the meantime, you can give them acetaminophen (such as Tylenol) for the pain if needed. Remember to always monitor their overall condition and seek medical advice if necessary.