My bottom eye lid is swollen and it hurts what is it?

Could be: Could be a sty or skin infection. Best to see someone right away.

Stye: You most likely have a stye. This is a localized infection of the eyelid skin. This will typically respond to warm compresses several times per day for a few days. If the infection starts to spread beyond the eyelid, then contact your ophthalmologist. Occasionally, oral antibiotics are prescribed to help with this.

Possibly infection: You could have the start of a hordeolum (stye) or even cellulitis which needs to be treated with oral antibiotics. See an ophthalmologist.