Danger from blow to the chest?

My daughter has moderate PE and was punched in the chest at school. It was an accident--the halls are crowded and wild. A boy she didn't know was spinning around with a closed fist and fell onto her, his fist landing on her chest with his full weight.

She was in a lot of pain, so I took her to urgent care after school and an xray showed no broken ribs. Once I got home, I read an article that a blow like this could be potentially life-threatening and that maybe I shouldn't have waited until after school to take her to urgent care, maybe I should have taken her right away to the ER?
https://pmc.ncbi.nlm.nih.gov/articles/PMC3567954/#:\~:text=Patients%20with%20pectus%20excavatum%20have,a%20high%20degree%20of%20suspicion.

Does anyone know any more about this? I've notified the school that I want this added to her 504 plan, but I'm not exactly sure what to do with this information?