Try this:-
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF BEGINSWITH[cd]%@", @"n"];
NSString *yourValue=@"nndfj";
BOOL result = [predicate evaluateWithObject:yourValue];
if (result ==YES)
{
NSLog(@"Word begin with n");
}
else{
NSLog(@"Word does not begin with n");
}