IsVeryScared,
The coloration of the lump is concerning. Dark green in color could be from an infection (pus) or could actually be stool under the skin.
You may be developing a fistula, where a tunnel forms from the rectum or anus to the outside skin (usually coming out somewhere around the anus).
Though some references say that these do not necessarily need treatment, that they can be "lived with", most people desire to have them treated. That would require being seen by a colorectal surgeon.
You could try using a warm Sitz bath, to see if you can get the tract to open and drain. This would alleviate some of the discomfort and may allow the tract to heal. But, it would not "cure" the problem and it may recur over and over.
You really should probably see a physician for an evaluation. If you live in a large city, which has a medical school, they often take cases pro-bono. Also, by law in the US, an ER cannot turn you away, just because you cannot pay.
Again, you should probably have this looked at. If you develop a fever, chills, malaise, etc, these are signs of a systemic infection, and then you would have to be seen. Good luck.