I have a white bump on my eyeball & it's irritating. What could it be?

Pinguecula. This is most likely a pinguecula, if irritated can use artificial tears or mild steroid drops. You need to protect your eyes from sunlight with sunglasses.
Benign Growth. A common cause for bumps on the skin of the eye (conjunctiva) is a benign growth named pinguecula. If this growth begins to invade the clear window of the eye (cornea) it is named pterygium. There are other less common causes for bumps on the surface of the eye. An eye examination to define the bump is important.