Any person complaining of anything done or omitted to be done by any stockyard owner, market agency, or dealer (hereinafter in this section referred to as the “defendant”) in violation of the provisions of this subchapter, or of an order of the Secretary made under this subchapter, may, at any time within ninety days after the cause of action accrues, apply to the Secretary by petition which shall briefly state the facts, whereupon the complaint thus made shall be forwarded by the Secretary to the defendant, who shall be called upon to satisfy the complaint, or to answer it in writing, within a reasonable time to be specified by the Secretary. If the defendant within the time specified makes reparation for the injury alleged to be done he shall be relieved of liability to the complainant only for the particular violation thus complained of. If the defendant does not satisfy the complaint within the time specified, or there appears to be any reasonable ground for investigating the complaint, it shall be the duty of the Secretary to investigate the matters complained of in such manner and by such means as he deems proper.