My child tried to do a front flip on the trampoline and and landed hard on her back and hit her chest, she is still having chest pain two days later, should we go to the er?

I would hate to expose a kid to the type of contagion and trauma that comes through an ER. The event likely produced some musculoskeletal trauma that may include rib injury. An urgent care center with x-ray capability or her regular doc would be a good venue. Cool compresses over painful areas will help. If she can't sleep, take her in.

A heating pad and NSAIDS are often effective in reducing musculoskeletal pain. If there is any breathing difficulty, please see the Emergency room. Otherwise schedule a visit soon with your Pediatrician or urgent care.