What Causes Large Yellow Pins On Thumb After Ligament Reconstruction?

Six weeks ago I had ligament reconstruction tendon interposition arthroplasty with capsulodesis on my left thumb. Since it has been six weeks, I am due to get the cast off, which I am looking forward to, this week; however, I also have two pins in the thumb and am a bit apprehensive about having those removed. The have large yellow heads, about the size of a pencil eraser, so if anyone can give me an idea of what to expect that would be great.