Andrew Tate's attorney is downplaying the alleged injuries Tate's girlfriend says she suffered at his hands ... comparing her post-concussion symptoms to a kid complaining to a nurse about a tummy ache.

Tate's attorney, Joseph McBride, tells TMZ ... Bri Stern's "post-concussion syndrome" diagnosis from a doctor's visit amounts to a kid going into the nurse's office at school and saying their stomach hurts.

McBride notes the diagnosis was not based on blood tests and says it's an "all-inclusive umbrella diagnosis which is very subjective."

Bri's attorney, Tony Buzbee, fired back, telling TMZ, "That’s the type of ignorant stupidity I would expect would spew from his idiotic mouth. I’m not in the business of responding to fools."

Bri says she went to the doc a few days after Andrew allegedly attacked her during sex ... she says he choked her with one hand and beat her face with the other.

Tate's lawyer says the doctor just diagnosed Bri based on the symptoms she claimed to be suffering from ... and he says it's similar to a kid who keeps telling a nurse their tummy hurts and wants to go home from school, and the nurse abides.

Bri accused Andrew of sexual assault in a police report and a lawsuit ... but he's vehemently denied the claims.

Andrew's lawyer is doubling down here ... saying Tate isn't dumb enough to rough up a girlfriend after some serious legal issues over in Romania.

Bri included alleged texts from Andrew in her lawsuit ... she claims he threatened her with violence and told her he would kill her if she ever crossed him ... but Tate's lawyer says the conversation is "doctored" and "manipulated."

Bottom line from Andrew's lawyer ... Tate did nothing wrong and they're gathering witnesses and information to prove his innocence.