pimple like bump on 5 month old help!!!!

Jacqueline
Hey ladies! I was changing my 5 month old diaper and I noticed she has a raised pimple like bump right above her butt crack. I've been reading that if she gets a fever at all that I should take her in to the doctors. Only thing is tomorrow is sunday...
So if god forbid I have to take her in would I do ER or Urgent Care?