Certifications required for a circuit board/ product
The type of certification will depend on the product you are selling, so getting in touch with a certified test agency to help guide you through the process is highly recommended.  Each country or region you sell into will have its own set of requirements (ie, hoops) to jump through to allow you to legally sell into that region.  For instance, even though the module you are using has an FCC ID for the module's approval, you may still have to test your product to ensure the product's unintentional radiation still falls within expected limits for US operation.  There are also potential safety requirements, EMC requirements, and labeling requirements.  This can be a daunting task to do on your own if you've never done it before, so finding a reputable expert or full service test agency is the way to go.