Shall I tell My Mom about what is happening here?

Sanchuz
Though My Sister don't want me to tell this to Mom, she didn't clearly tell me what is her relation with that Guy, he Claims she is his girlfriend, but in the beginning she told me like he and his friends are bothering her So i tried to intervene and help My Sister but those Guys beaten me and he butt fucked me ( forcefully) and has threatened me not to interfere into his matter with my sister else he would do it Again, Now I want to tell to My Mom about what is going on here but My Sister is stopping me, She is saying if i told to My Mom then it would become more Worse ! i don't get her Point here? shall i tell her or Not?

below is My First question which i has asked for this Issue, You may go through for more details

Shall I Not intervene into his matter with My Sister? Will he leave me if I Apologies from him ?
Updates
+1 y
My Mom lives in other town, 2 years ago my sister had come to this city for her Graduation, I came here just few months ago, if I tell My Mom about what is going on Here then My Mom Might ask my sister to come back to home, Which my sister don't want and that's why my sister don't want me to tell to mom, but When i still wanted then my sister got annoyed and she has warned me that if I tell my mom then it can annoy him ( her boyfriend ) and his friends and he can butt fuck me Again !
Shall I tell My Mom about what is happening here?
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