Epidermal cyst

A epidermal cyst is a closed sac under the skin filled with a cheese-like or oily, semi-solid material called sebum.

Sebum is produced by sebaceous glands of the epidermis.
A foul odor is also often present in the substance called keratin which fills sebaceous cysts. Keratin is a protein that creates the sac of cells called epidermal cysts.
The bumps or lumps that can feel under the skin are actually the sac of cells.
Many homeopathic medicine can help in such a case like bufo, cuprum-ars, rhus-tox, rhus-ven, thuja, petr, chel,calc-phos, zinc etc.
To select a remedy, more information about a case is required.