You really have no choice - you must get checked by a doctor. It is possible something has happened to your anus that could cause you problems later, perhaps serious problems...
In order to avoid that it is important to get such quick and dramatic changes checked as soon as possible.
If you feel you cannot go to your own doctor there might be an accident and emergency department nearby or a sexual health clinic or a family planning clinic.
If you really cannot get to a doctor, do you have a community nurse you could talk to?