There are different forms of cysts. But the one that occurs behind the ear is mostly epidermoid cysts or pilar cysts. Rarely, what you have might be a sebaceous cyst.
Some lumps can resolve without any form of medical intervention. For instance, you can treat mild injuries from home. But some cases will require medical intervention.
If your lump has a fleshy feel and is on the top of your skin, instead of beneath it, you could be dealing with a mole. There is hardly anyone who does not have any mole on his or her body.
The most rampant cause of neck lumps is lymph node enlargement. Treating a lump on the neck will depend on the root cause.