Why does my heel hurt after/during running?

ok so a couple weeks ago i had volleyball camp for a week and towards the end of it i started getting slight pain in my heel while running and even walking, putting weight on it. mostly when my heel would go up while walking/running. i rested for a while after and recently started running again. it hurts a little while i run but mostly hurts after. i was walking around after running and it hurt. i tried running again and mostly the same thing happened. the pain usually gets better through the day. the thing is, i am going to a sleepaway sports camp a week from now and i need my heel not to hurt while i run! what can i do? stretches, ice it, etc? what might this be from and how can i prevent it? i also have pre-season tryouts for volleyball in around 1.5 months and i have to be better by then. PLEASE HELP! my heel needs to get better! thanks!