What Could The Indentation On The Top Of My Skull Be, Given My History Of Kidney Transplant, CKD Stage 4, And Current Medication?

Hello, I am a 54 year old female hx of kidney transplant post 5 years. I’m on cellcept 1000mg daily , Envarsus, 2 mg daily, and 5mg of prednisone. Kidney disease from glomerularsclerosis. Current CKD is stage 4 due to chronic humoral rejection. I am diabetic controlled. Recently I found an indentation on the top of my skull above my forehead just to the left of center, running vertically back about 2-3 inches. What could this be