Painful Lump on lower back

Patient: For over a year now, I have had a lump, about 2×2 inches in length & width, under my skin on the very lower, right portion of my back. Today I woke up, and the lump has felt like it has slightly grown, and now feel a moderately painful sensation when I touch it. Is there any idea as to what this may be, because it is quite concerning. Thank you.

Symptoms: Painful to the touch

Doctor: