ER said hairline fracture, orthopedic doctor said bone wrinkle?

My 5 year old slipped in the mud and hurt his arm. Four hours later he's crying it hurts too bad to sleep. I took him to the ER and the doctor there did xrays and brought them in and showed us a small crack that was only visible in one the angles. She referred us to an orthopedic specialist for a cast and they went ahead and splinted it up for him. I made the appointment with the orthopedics and he came in room removed splint, pushed on my sons forearm all the while he's telling him ouch, that hurts and informs me the ER wasted my time he doesn't need a cast that sometimes they mistake bone wrinkles for cracks and i should just throw away all the splinting material. here it is night time again and my little boy is again complaining of the pain. Should I look into a second opinion? and what is a bone wrinkle? I've tried looking it up but all i find is facial issues.