What Causes Lumps On The Nails Of The Fingers?

My thumb on the right hand, my ring finger and small finger on the left hand, have 'lumps' on the nails as they are growing out. I have not had an injury to these fingers. Can you please tell me if I am deficient in something? I am 59 years old, am 5'1" tall, weigh around 54 kilos. My general health is OK, although I have IGA Nephritis which is being monitored with no treatment required as yet. I have high cholestoral and am taking Crestor for this. I am also taking Lovan (for depression).