Making yourself throw up sometimes is not that harmful and sometimes we need to make ourselves throw up such as if we ingested poison accidentally or our stomachs are feeling bad and we need to throw up to relieve the upset stomach.
So in that case making yourself throw up when needed is okay.
But it's not good to make yourself throw up if you don't need to throw up because it can put more strain on your esophagus which can lead to tearing of the esophagus.
Those tears are esophageal tears also known as Mallory-Weiss tears, and cause you to potentially start throwing up blood which is not good.
So avoid making yourself throw up unless you really need too.