Last Monday, My 17 Year Old Daughter (a Cheerleader )

Last Monday, my 17 year old daughter (a cheerleader ) was dropped on her tailbone in practice. She was diagnosed with a concussion and has had a constant headache, sensitivity to light, etc. Tonight, she said her right side of her lower back was sore (it always had been, but since her neck pain is better, she says she notices her back pain more now. Anyway, I noticed a large slightly bruised/swollen area on the right side of her back. The school (where the injury occurred) is hesitant to run any imaging like CT Scan or MRI of the spine. But I'm concerned. Thoughts?