I woke up yesterday with a golf ball size bump on the back of my head ?

Bump: If it is literally that large, would ask is it red, tender, warm, painful? Purulent drainage? Do you have a fever? If yes, you may have an infected cyst/ abscess. On the other hand if it is down a little bit further, and not really quite that large then it could be an enlarged lymph node. Your doctor should be able to diagnose it & determine what action needs to be taken.