A red, swollen bump at the eyelid that looks like a pimple, and, is tender, especially to the touch, is probably a stye (an inflamed oil gland on the edge of the eyelid).
Styes are caused by a bacterial infection, when the bacteria grow in the root (follicle) of an eyelash.
Some people are prone to frequent styes.
If the bump feels harder and is located inside the eyelid, the diagnosis is probably a chalazion.
Visit your ophthalmologist for correct diagnosis!