What kind of glue did you use? If it's really on there and doesn't want to come off, I would make sure it's stable and veneer over it. If you used PVA wood glue or hide glue of any kind, use a clothes iron. If you don't want to mess up the one you have, buy one for the job (rummage sale, or Walmart has them for about $12). This should work for contact cement, too.