ACV or castor oil won't do anything to reduce cysts - you need to see a dermatologist and get it examined (in case it may be a tumor instead of a cyst) and removed.

Surgery on a cyst is much simpler when they are smaller, and the removal of the bad tissue will allow your body to heal. As long as the cyst remains, it will continue to get irritated, infected, and continue to grow. Without removing it, you may also create a permanent bald spot.

Surgical removal consists of numbing the area around the cyst, and it's removed and the placement of a few stitches (often placed under the scalp, so they can't be seen) - when the numbing agent wears off, it's usually an itchy sensation with minimal soreness. Much easier to do this now than to continue with increasing pain/swelling/infection by ignoring it.

Good luck, please keep us posted.