First, you'll need to get the panel off under the hopper to get access to the auger motor etc. With the auger motor removed, you should be able to get access to the end of the auger shaft itself.

With a pair of pliers or mole grips try and grab the end of the auger shaft and turn it counterclockwise while pulling backward. This may get the auger out. However, if your pellets got wet and expanded in the auger tube this probably isn't going to work. 

In that scenario, you're really going to need the assistance of a power tool such as an electric drill. Lock the drill onto the end of the auger shaft and gently turn the auger anti-clockwise while gently moving the auger forward and backward.

This will not only remove the auger from the blocked auger tube, but you can also use the auger on the end of the drill to clean out the hard sawdust in the auger tube.