A chalazion or stye is a blocked gland on the eyelid, similar to a pimple on the face. It is most often treated conservatively with lid hygiene (scrubbing the eyelid with baby shampoo) and prescription medicine. If a chalazion does not respond to conservative management it can be drained surgically.
https://www.aao.org/eye-health/diseases/what-are-chalazia-styes