How do i know what a blood clot in finger looks like?

Circle of blood: A small circle of blood (a clot) under a nail - from trauma - is unsightly but not dangerous. With no treatment it grows out in a month or so. In an emergency room - completely painless - no anaesthesia needed - a doctor can burn a hole (with a hot paper clip in the nail and drain the blood completely. The hole grows out in a month. Peter wilk, md.