I have a large painful squishy lump on top of my head, haven't had any recent head injury, its been getting gradually larger and more painful.

Examination: You need to make an appointment with your family doctor or a dermatologist to have this area of your head examined.

Likely benign: Possible sebaceous cyst, and unlikely to represent any type of tumor, but since this may be a localized nidus of infection, not a bad idea to have examined and perhaps excised, usually a simple outpatient procedure.