I have a hard bump on my nuchal ligament. it feels like bone and doesn't hurt, but i have headaches that are probably caused by tmj?

Could be TMD: Temporal mandiblar disorder can have headaches associated with it. The area you describe can sometimes be a 'trigger point' for the disease.

Yes: The nuchal ligament connects to the external occipital protuberance and the pull on this ligament from a forward head posture can cause this bone to grow. Studies have shown that TMJ patients present with a 4 inch forward head posture on average. The bony bump is not a concern but usually what is going on with the cervical spine and tmj. See a dentist who treats TMJ for diagnosis and treatment.

Probably not TMJ: A hard bump on your nuchal ligament that feels like bone not related to TMJ. I'd start with an evaluation by your MD, and then referral to the appropriate specialist.