Table column filled later on

I'm new on Laravel and as I'm playing around with it I encounter this issue. I have a registration system which worked fine but now I wanted to add a new field in my table (description field for users). However, this description field, I don't want to be filled when the user signs up, I want the user to fill this when he gets on his profile and updates a modal window.

The problem is, if I let that filed empty, I get an error when I sign up saying that the description filed can't be empty.

This is what I use in my UserController in order to update the description field but I'm not sure if is correct.

public function postDesc(Request $request){
  $this->validate($request, [
    'description' => 'required|min:20'
  ]);
  $user = User::all();
  $user->description = $request->input('description');
  $user->save();
  return redirect()->route('user.profile.edit');
}

This is how I opened the form: {!! Form::open(['method' => 'PUT', 'action' => 'UserController@postDesc', 'class' => 'profile-form']) !!}

via Chebli Mohamed