Yes, you can commercialise or use your invention without patent protection. However, once your invention is made known to the public, you may not be able to obtain a patent if you decide to apply for protection later.  It should also be borne in mind that apart from a patent, for certain industries, there may be legislative requirements governing the use of an invention. For example, if your invention relates to a pharmaceutical product, prior permission must be obtained from the relevant health authorities.