You could be held liable for selling defective products to a consumer who later sustains injuries from something bought at your store. Once people are in possession of your product, you cannot stop them from injuring themselves. You can control this third element, however, by making sure that any item that leaves your control does not contain a defect. Your only protection is insurance.
Many defects are detectable before an accident occurs if the right tests are made.
Courts have held that manufacturers have a duty to inspect and test their goods. Failure to adequately test has been held reason enough to impose large awards of punitive damages on top of the actual damages awarded. Sophisticated testing might prove to be too expensive for the small business. Ideally, you should design the best test you can for whatever you make, even if it is only a good tug here and there. Most importantly, keep a record of what tests you conduct.