I had a painless lump on my buttcheek for two years no changes until a couple days ago it became painfully and inflamed?

Infected cyst, to MD: It sounds like you have a cyst, which is common, and now it has become infected. This is also not a rare event. Please see a doc for treatment ASAP, rarely antibiotics may be enough, but almost always, the infection needs to be drained. Do not pop or squeeze it yourself! You can make things worse. If you have fever, red streaks, marked increase in pain, go to an ER.