Sorry but this is not a cud. A cud involves the rim of a coin when a portion of the die breaks away from the edge. This is either a minor die chip or displaced metal from a hit to the coin.
Like @tommyc03 said, it looks like a very minor idb. Internal die break. I get a lot of information from http://cuds-on-coins.com. You can compare your coin to others that are listed. It's a very nice site to use as a cross reference if you are unsure.
