Nano materials are not a specific hazard class within GHS or within CLP. In the EU, nano materials are required to be described as such in REACH registrations, see https://echa.europa.eu/-/reach-guidance-for-nanomaterials-published . ECHA have also launched a “nanomaterials observatory” in June 2017, https://euon.echa.europa.eu/, to provide people with information on nano materials in the EU, which may be a precursor to regulating them specifically throughout the EU.
Nano materials have been designated in some individual countries in the EU, such as France and Denmark. In these countries, extra rules on hazard communication may apply, and you should check the guidance for these countries to ensure you are meeting their individual requirements.
Other jurisdictions, such as Australia and the USA have started to regulate nanomaterials specifically.
The main problem with nano material regulation is defining them in a sensible way, which is proving quite difficult and even controversial, as powders such as wheat flour can be included if the definition is made only on particle size or particle size distribution.
At the moment, it is recommended that if you are making materials which could come under the nano definition (e.g. fine powders, such as pigments), and you are selling into countries which have nano material legislation, you should comply with their rules and guidance on a case-by-case basis.