Why do sleeping pills effect me so much?

A while back a pain had surfaced on the elbow of my left arm. The pain was unbearable, and i convinced myself it was nothing. I am 15 and my parents went out of town and my cousin came in from another state to watch me. The pain in my arm got worse and i couldn't sleep correctly no matter what i did. Pain relievers didn't work but my cousin said this is a good pain reliever and i didn't know because i was tired but couldn't go to bed. So then i swallowed the pill with assistance of water and i layed back on the couch. A couple minutes later i just went down. Does any one know what caused this pain in the first place and was it growing pains possibly? And we did the sleeping pill knock me out so quickly even through the pain? thanks