rash/red bumps on my 1-1/2 olds cheek?

my 1-1/2 old has had this "rash" for about 6 months. it started off as one red bump that the DR said was a bug bite then two months later it turned into several little bumps and it hasn't spread anywhere else. sometimes the bumps look red and puffed up then sometimes you can barley see them. the DR doesn't know what they are and the dermatologist want to biopsy them. hope someone can help.