Jasleen: Surely, Content Marketing is a fast growing field and is one of the most sought after skills in digital marketing. I don't think there's is any popular or credible industry certification for content marketing. At the same time, while certifications such as Google Adwords and Hubspot Inbound Marketing have certain value [i.e. a.) differentiate from others who don't have it b.) preparation for the exam ensures that you've acquired the knowledge], your focus should be really on acquiring practical skills around various aspects of Content Marketing.
Those skills and the confidence you will gain out of acquiring those skills will play a real role in accelerating your career in Content Marketing.
Btw, Content Writing & Content Marketing are 2 completely different areas and it makes natural sense for a Content Writer to grow to Content Marketer to grow in his/her career.
Hope this helps. Let me know if I can be of any further support.