I think the actions taken were appropriate. The abuse was reported.
There was no threat of additional harm to the child other than progression of the inital injuries. OP did not witness abuse, nor is she a medical expert who can determine the cause of an injury. She can reasonable conclude it was the result of something other than a fall, so as a mandated reporter, she was obligated to report it--which she did.
The child was taken to the hospital, and OP took appropriate steps to call the hospital and CPS to report her suspicions of abuse--particularly timely to do so while child is enroute to the hospital.
Kudos to OP for handling the situation well.