I Have A Pea Sized Lump On The Bone In

I have a pea sized lump on the bone in my wrist the opposite side to the pisiform bone so thumb side not little finger. I is swollen and painful and feels like a jab if I put pressure on anything with my hand. I can twist my wrist and the liggerment on top of the little lump twangs but the lump doesn't move. What is the lump likely to be?