A lot of the commonly used social media apps and sites have ways to report abuse, threats, and hate speech, etc. although they each have their own way of doing it. Some generic advice involves reporting it even if you think it won’t amount to much because that report will still be linked to their profile if something happens later on. Also, while most of them have predetermined selections you can make about what kind of report you are making, if there is a spot to type why you are reporting, it should be done with as much specifics as possible.
Learn how to report abuse from the Online Harassment Field Manual, or read this article on CNET.