Suggest Treatment For Boils Between Buttocks Of Baby

My 13 month old grand baby has 5 boil looking bumps on the inside of her butt cheeks. one week ago there was one, it oozed greenish thick stuff, it was still hard and hot feeling, then over this weekend 4 more of the same type of bump came up in her crack. they are really hard feeling down deep in her butt and they are deep dark red and very hot and fevered. She can t sit her on bottom and she cries when you hold her in your arms. I know she is in pain. What could this be. This all started out as a bad diaper rash almost 3 weeks ago. we took her to the emergency room and they gave us nyostatin for the rask