The other day I bought some 1x4 lumber for the trim around the door and windows for the playscape we our building our boys. I had one of them, so I had the Home Depot NASCAR-certified race car shopping cart, which doesn't leave much room for lumber.
When I was maneuvering the cart around the van I kicked the end of the 1x4 stack with the side of my calf. I felt a jolt, but I figured I must have hit the corner of the wood. Later that night and the next day it was itching, but I thought it was just the scratch.
Then I felt my leg and I could feel something under my skin! Nothing was showing on the outside, so my wife (whose sister is an accomplished surgeon so maybe something runs in the family...) started working on my leg. Below is what was in my calf with a penny for scale. None of the splinter was outside my skin!