What did the bird look like which you saw exiting from the hole? Other birds will use woodpecker roosting holes (wrens, nuthatches).   You should repair the holes as soon as possible. The presence of a hole is a visual attractant to woodpeckers.

Here are several ideas for discouraging further woodpecker damage.  Hang some shiny, reflective plastic plates or long shiny mylar stripes in the area around the holes. The strips or plates should be able to swing freely in the wind.

Another tactic is to provide roosting boxes for the birds nearby so that they won't drill any more holes.

Finally, plastic netting may be hung to cover the area where the birds are pecking.

Please keep in mind that woodpeckers are a protected species.

Here's a link to Cornell University Laboratory of Ornithology for more detailed information:

http://www.birds.cornell.edu/wp_about/index.html

If you are persistant, you should be able to prevent more damage without harming the birds. 

Please feel free to contact me if you need any more assistance.