I Have A Small Pea Size Lump Under My Skin

I have a small pea size lump under my skin on my elbow. My whole arm hurts, it even wakes me up at night. The lump has gotten smaller, and it does not hurt to the touch, but my elbow hurts and it makes the rest of my arm hurt. I have had it now for 3 months. I have no insurance, what kind of tests will I need