I was prescribe sumavel dosepro for migraine & got a dose in my arm by my doctor but pamphlet said not arm what can happened?

Probably ok: The injector uses air pressure to inject the medicine into the fat under the skin, so the manufacturer recommends the belly fat area (because everybody has fat there). Most people have fat on the back of the upper arm, so there's probably no noticeable difference if injected there compared to at the tummy. If injected in the arm skin where there is no fat, perhaps more or less drug gets absorbed.