My three-year-old has been complaining today that her back and side hurt. I thought she pulled a muscle or something so we iced it. Before she went to bed, she told me that it hurts when she goes pee pee. I checked and it was red. Are there any home remedies for a UTI (I'm assuming that's what it is) or do I absolutely need to take her to the pediatrician for antibiotics tomorrow morning?

I heard cranberry juice is good at preventing UTI's but not necessarily treating them. Any other suggestions?