1) The store is only potentially liable IF you can show that the store was unreasonably careless in some way--such as by not setting up the stand properly, which is why it fell. If the store did nothing wrong--if, say, the stand feel because your son hit or bumped it, or someone else knocked into it--they are not liable. Liability depends on fault.2) Even if the store is liable, you can only recover an amount equal to your out-of-pocket  (not paid by insurance) medical costs, and for injuries which cause a *significant* life impairment or disability lasting many weeks or more, some amount for pain and suffering. For the injuries you describe, none of which are long lasting or permanent and which do not seem to "signifiantly" impair life, the amount of money you could recover would be very small--possibly less than the cost of the lawsuit (given that to recover for personal injuries, you almost always have to hire a doctor or other medical expert to testify about the cause, severity, impact, and prognosis of the injuries).