Here's the deal ... Blac Chyna got the Los Angeles Department of Children and Family Services to investigate Rob after Dream suffered multiple burns at his home, and she claims Rob initially denied the second burn happened under his watch.

Now, Rob is firing back and blaming his former nanny while also chiding BC for trying to smear his name.

Rob's attorney, Marty Singer, tells TMZ ... Dream's health and well-being is Rob's top priority, and even though Dream did in fact get burned in two incidents with the nanny at Rob's home last month, Rob's confident DCFS won't find any safety issues at the home.

RK's legal team tells us the nanny is leaving his employment, and they say Rob treated Dream's incidents appropriately and told BC what happened.

Rob's attorney tells us it's "unfortunate that Chyna feels the need to publicly miscommunicate the situation and has once again wasted valuable public resources by calling first responders in a desperate attempt to smear Rob’s name in response to his ongoing lawsuit against her for full custody of their daughter."

And, get this ... Rob's attorneys say he has grave concerns about Dream's safety in Blac Chyna's care, and they say third parties have sent DCFS to BC's home for her treatment of Dream.

Dream's come back from her mother's house with many unexplained injuries -- rashes, cuts, bruises and a dislocated arm -- at least according to Rob.

Rob's also blasting BC for claiming to be concerned about Dream's safety when she was busy posting a video showing Dream on her older's back while they were bouncing on a trampoline.

As you know ... Rob and Chyna have joint legal and physical custody of Dream, but their both gunning for primary custody.