Greetings Sir/Madam.
I am glad that i am able to help you to overcome your problem.
My opinion after reading your query is that probably it might be any previously unnoticed birth mark/ trauma/the area is infected.
But since the swelling hasn't moved and giving you discomfort viz., pricking/pain sensation when you sit down, some serious thing happening inside.
Just answer following questions:
1. Have you got any fever?
2. Has the swelling ruptured and reappeared or just increasing in size?
& understand that i can't ask more here.
If it feels very discomfort for you, It's advisable to kindly get examined by a Family Physician/
General Surgeon in order to find out the exact nature of your problem(or any other problem causing you trouble in that area mentioned viz., Piles etc.,) & get treated accordingly before it gets complicated .As i haven't seen personally, i could do this much only viz., guide you.Hope you understand.
And coming for home remedy as temporary measure(to overcome pain), follow these simple steps:
1. Take
cold Shower instead of hot bath.
2. Eat green vegetables viz., salads; oat meal
3. Drink plenty of water viz., minimal 8 glasses/day.
4. Maintain proper Hygiene of genital area viz., Clean the affected area with soap and water.
5. Then if pain in anus, take a SITZ bath(a warm, shallow bath with salt added that cleanses the space between the
rectum and genital region) can be used for everyday personal hygiene & also it provide relief from pain or itching in the genital area.You can give a sitz bath in your bathtub also.
&
Finally,
Approximately 30-50% of people with an anal abscess(an infection happening inside your existing swelling which rupture) will develop an anal fistula(an abnormal or surgically made passage between a hollow or tubular organ and the body surface, or between two hollow or tubular organs).
Around 80% of all anal fistulas develop from an infection already in the anus.
Consult your Doctor if you feel uncomfortable in spite of above measure before it gets COMPLICATED.
Hope i guided right & it helped you.