Like inhaling anything, it's not safe. The only thing for sure is that your lungs will probably have the burnt plastic in them for a while. See your doctor if you feel it's necessary, otherwise you'll be okay. If you experience shortness of breath, see the doctor IMMEDIATELY...that could be a serious problem.
If it's just a plastic fork, call the manufacturer and see what they say. They can probably tell you what's in it, and what will happen from accidental inhaling. You will, most likely, be perfectly fine.