The answer is stratum basale
Epidermis is made of 5 layer of skin. The deepest layer of epidermis is called stratum basale. The cell in this layer will keep dividing and move to the upper layer. Since the cell is dividing, you will find nucleus inside the cell of this layer. Upper layer of skin slowly become keratinized and lose their organelle.
The two main layers composed in the skin are the epidermis and the dermis.
The epidermis is the superficial layer of the skin and is composed of four to five layers depending on the location of the body.
These layers are; stratum basale, stratum spinosum, stratum granulosum, stratum corneum and a fifth superficial layer located only on the palms of the hand and soles of the feet, called stratum lucidum.
The epidermic layers ranges from deep to superficial, with the deepest and fifth layer being "stratum basale" also called the "stratum germinativum" which is just located above the layers of the dermis. And in this case would be the fifth layer the splinter would penetrate and then injure.