Big, hard lump at the base of my skull- pilar cyst? Or what?

I (F21) woke up this morning to a slight ache at the back of my head. I go, touch around, and find what feels like a firm, tender, 2 cm big bump at the base of my skull. I'm trying not to freak out because of it, so, is a pilar cyst most likely? It feels a little softer than bone but not by much. I tried taking a picture, and though it was hard to pinpoint, I think the bump is a little red.

Any ideas?