Lucas,
Thanks for using JA! How old are you? Any other medical conditions or take any medications on a regular basis? From the sounds of it, it is probably an Anal Fissure, a small tear in the anal canal. It's usually caused in adults by an unusually large or hard bowel movement. Most of the time they heal by themselves with no complications. If you need you can use Anusol or or an over the counter cream or ointment containing hydrocortisone like Cortaid or Preparation H to help with any discomfort.
I hope this was helpful, please remember to leave positive feedback.
