Hey just want to reassure you and anyone else who finds this post, I have one on the back of my ear I believe mastoid bone. It's immovable hard and feels big! I'm sure it had been there years but I just kept getting paranoid recently so went to the doctors then referred for an ultrasound she put it on and said 'oh my god it's tiny, the reason why you can feel it is because it's sitting on the bone but it's a tiny, perfect little lymph node. Nothing sinister so please go home and enjoy the sun' honestly I was over the moon! I said I was so worried because I couldn't move it she says but you can't normally move them... so I hope that helps anyone who finds this post!