There’s a convenient method for that by the name of substringFromIndex. This example removes the first character:
NSString *complete = @"12345";
NSString *cutOff = [complete substringFromIndex:1];
// cutOff is now 2345
substringFromString takes only one parameter which specifies where to start the new string. The first character is 0 based, like in arrays. The parameter can’t be longer than the original string’s length for obvious reasons.