omg, what is going on?!

My boyfriends sisters baby has a butt cheek that became very swollen, hot, and hard to touch yesterday. During the middle the day, the baby was experiencing very high fevers and her body was burning hot. Towards the end of the night, my boyfriend noticed blood around the area, hes unsure whether it is coming from the cheek or the hole. The babys mother refuses to come home and do anything about it yet. She is the only one with a functioning car. What do you think is wrong with the kid?