Need advice now_At ER_ SO's son injured_absentee mom shows up

Emma • "In a perfect world, you could fuck people without giving them a piece of your heart... every glittering kiss and every touch of flesh is another shard of heart you’ll never see again." Neil Gaiman

SO's son was badly injured and was at the ER crying for ME. Two hour drive from work I get here and absentee mom is here and picks a fight. (Hasntseen him in a year!) Pphysically pushes me! Definitely not my style. Makes baby boy cry more. SO and I just broke up in the past couple days. Do I stay for the boy?

I want to! But is it the right thing? Ahhh! Not sure what do.