In my humble opinion, it is still wise to find out the cause of your child’s stomach pain. In my experience, some of the more common causes include (but not limited to) non-specific abdominal colic, constipation, stomach flu and even appendicitis (which is a surgical emergency), etc.
Simple symptomatic medication such as Colimix can be purchased off the counter at any retail pharmacy.
If in doubt, please do not hesitate to visit your GP or a Paediatrician for a detailed consultation.