My eye hurts and there is a swollen bump inside my lower eyelid. what could be the cause?

Stye: At your age, this is probably a stye. This is a blocked gland in the substance of the lid which will produce a red swelling on the inside of the lid. If advanced it may swell the whole lid. To treat, use very warm washcloths socked from your water tap (not too hot). for about 5 minutes at a time, 5 times per day for several days . this will usually get rid of it.