Re: sebaceous cyst?

 If you mean under the skin rather than part of the skin then I would agree it is likely a cyst.  And if it is a cyst what I would do personally is numb the area with some ice for a while then stick a hyperdermic needle in to it so it can drain.  Cysts are fluid filled sacks.

Silica and vitamin C would also be good internally to help strengthen the tissues and reduce the irritation and inflammation.