Kim,
How tacky is it? If its just firm but sticky, I would expect you would be able to pop it out, especially if you used a mold release.
If that isnt possible, I would try some industrial strength acetone (e.g. from a hardware store) to try to get it out. Just a warning, this may damage your mold and you should wear gloves when doing this.
If your resin is a gooey mess, than Im afraid its going to be about impossible to get the resin out without causing yourself a lot of aggravation.