Had a molar extracted and bone graft done about 3 months ago. Now my jaw bone is poking through gum.

sometimes sharp legdes of bone could poke thru thin gingiva or this could be because if bone sloughing off as a result of healing compromised due to some medications Go back to your surgeon , specially if this has been there for a long time and is naking your tongue uncomfortable. The sharp bony ledge could be filed down. So then the gum would have a chance to grow over it.....

It happens sometimes, that the bone particles or pieces of bone make through the gums and start poking you.  In many instances it does not indicate a bone graft failure.  Just go back to that dentist, to evaluate it.  It's a  very easy fix, bone can be smoothed out and the gum can grow back, and you will not feel discomfort anymore.  Different people heal differently. 

It's not unusual after having an extraction and graft to have small particles of bone come out through the gum.These particles can be quite sharp and if you need to have them removed, it's a very easy procedure.I hope you pronounce information to be helpful,Dr. Champagne