What is this please help me I am freaking out

So a couple of days ago my daughter got this pimple on the sides of her back. I ignored thinking it was just some normal pimple or a mosquito bite. it started getting brown after some days I thought it got rubbed and now it's drying but slowly it started expanding and the area around started looking weird too. can someone please tell me what this could possibly be?

update: I went to the doctor today. it was staph infection and thankfully it hasn't spread. infact this is it healing. the doctor gave us an ointment.