Any use, structure or lot existing on April 22, 1958, or thereafter which was commenced while a previous zoning ordinance was in effect and was in violation of such ordinance shall not be a nonconforming use permitted to continue under § 745-4 but shall be a violation of this chapter, unless the provision of the prior ordinance which was violated shall have been changed by this chapter and such use, structure or lot is not in violation of this chapter, and no violations are waived.