i need major advice

me and one of my friend's had a major falling out. he mentioned that he #didn't agree with what i was doing" (but never specified what that was. he was extremely immature about the whole situation) and also that i had done things to hurt a mutual friend. i had no idea about this, so i had asked the mutual friend "hey have i done something?" that friend told me no. i thought everything was dandy with that friend. i got over my falling out with this friend pretty fast (even tho he talked about me very often i hear.) however, when i brought up that this mutual friend had hurt me they reflect it with "oh you did all this stuff" (that happened BEFORE i originally asked if i had hurt them.) and never took accountability for their own actions and never apologized. i apologized for every single fucking thing they said i did, point by point. i really wanna bring this up with my friend but i have no idea how to, and i'm worried if i do they'll hate me (which is not a good thing because i HAVE to see them alot and i do a class that they teach.) so please just like give me something i dunno how to bring it up