Is this a swollen lymph node ?

[Databey19]

I noticed it in the mirror and. I can’t tell if it’s my mastoid or a swollen lymph node ?

[RadioGaGa]

It's very difficult to tell via a picture alone. Besides, we cannot diagnose on here.

Anyway, make an appointment with your GP. In the meantime, generally on palpation benign nodes will move and not be rock hard.