I had a hard lump on my neck had it for months it got bigger and it burst and this thick green stuff came out and its smells?

Cyst or Abscess: Sounds like you have an abscess or collection of puss. I would have your doctor take a look at it to make sure it fully drains. Sometimes then need to be opened up to help fully drain.

Sebaceous cyst: You have a cyst that ruptured and drained. You will have this happen again. Best to see a general surgeon. Removal in clinic and be cured.