You should not let yourself get hungry. If you are it's a sign that you may not be eating enough throughout the day, if not at one specific meal. There really isn't enough information in your post to tell if you're eating enough.

A good rule of thumb is to aim for 10-12x your body weight a day in calories. This number will assure, all things being equal, that your body will have sufficient calories to maintain basal metabolic functioning - i.e., it will not think it is being starved.

You might want to consider keeping track of calories for a few weeks while you get a 'feel' for just how much you are, and aren't eating. www.fitday.com is a free site where you can register and track calories/macronutrients/ and weight. Many of us make use of it to ensure we are eating enough.

Keeping a journal on this site would also be beneficial - it would make it a lot easier for us to offer advice and troubleshoot if we could see just what your daily routine looks like.

HTH
Nat