Hello. I'm A 14 Year Old Male, And Yesterday My

Hello. I'm a 14 year old male, and yesterday my anal opening was starting to hurt. It did again today and I managed to try and get a picture of it with my phone to see what it was, and there was a dark purple and maybe blue ball, a little bigger than a peice of corn. I've looked and some people say it's a blood blister, and some say a hemeroid. Please help because I'm kind of freaking out about the whole thing.
Thank you.