Thanks for writing here.
Information provided by you classically supports the diagnosis of sebaceous cyst
.It is quite common in routine practice.
At times it gets inflamed and becomes red and swollen as in your case.
Ideally such cysts should be removed by surgical methods.Removal of capsule is must and it prevents recurrence.
As you have drained material at home there may be a chance of relapse of cyst.
It will be better to consult doctor
next time when cyst reappears.
Hope this will help you.Take care.