I have done my BMS this year and I want to work in digital marketing. Is it necessary to do any course for digital marketing?

While doing BMS, there would be some specializations like Marketing, HR, Finance, and others. So, if you had done BMS with Marketing specials, then you are good to go. But, if not then you have to do something, like special for marketing in Post-Graduation course or some Diploma will also be fine.