I'm a healthcare provider and I, myself, have used this phrase zillions of times. However, grammatically, I want some clarification on this.
The pain was all over the body - is absolutely fine and accepted. It means the patient suffers from pain everywhere in their body.
But why we use over here? Over makes better sense in this sentence
She was painted all over her body (in case of body painting).
She has rashes all over her body - this makes utter sense to me; she has rashes, on her skin, all over the body. It talks about the surface again!
Should I use this to sound grammatically correct? Just as we use over more for the surface (all over the place) and not something inside (body).
The pain was everywhere in the body OVER The pain was all over the body