Meibomian Cyst (Chalazion)
A chalazion is a slowly developing lump that forms due to blockage and swelling of an oil gland in the eyelid.
They are usually painless and aren't sore unless infected. Over time lumps gradually gets harder and as they protrude into the eyeball they can temporarily distort the cornea, resulting on blurry vision.
Most chalazions will self resolve without any treatment. Applying hot compresses and massaging the lump can help to dislodge the blockage within the oil gland ducts. If the swelling doesn't subside, a minor procedure can be performed to remove the lump surgically.
Excellent information on chalazions is available from the American Academy of Opthalmology website here