Hello and thanks for the query
Usually these lumps are benign and can not cause any problem. We have to worry if it starts increasing in size, aching or discharging. The best method to know what it is, is the biopsy
of the lump after surgery as your doctor advised you. But needle aspiration test (FNAC) can give you an idea about that. It can be done by you doctor if you are scared from surgery. But if reports came back something abnormal than you have again go for the surgery. Your doctor advice
you the best by clinical examination of the lump.