I have an access on my neck it's been there a week... last night a huge knot popped up on the back of my skull and it hurts badly.

Abscess? And pain?: I think that is what you meant to write here. This is a something that needs an in person evaluation right away if you have severe pain and if it is more than a small, superficial skin issue like a bigger pimple for example. Without looking at it, I have to be cautious. If you use injection drugs of any kind or are diabetic/have immune issues, get seen in the emergency room or urgent care now.