in nitration u add two concentration acids HNO3 and H2SO4 both are strong acids. always the acid base neutralization reactions are fastest. even though NH2 group in aniline is a weak base, its neutralization with a very strong acid is still faster than nitration. hence if u carry the acid base reaction u would end up with an NH3+ group. hence the meta substitution can't be rule out here and u would get all products ortho,meta and para...