Hello, for almost 10 yrs iv had these small splinter looking blood formations under my nails, they range from a single splinter to several per nail, and sometimes none for a long time. Iv heard that it can be caused by endocarditis and vasculitis, but iv had recent heart diagnostics done, and they said nothing was out of the ordinary, but the research iv done about the splinters also says that nail trauma can cause it, and I chewed my nails till i was 19 and im 25 now. I also have a nervous condition that makes me tap my finder tips and nails on surfaces if i dont keep my hands busy, could either the nail chewing or the nervous tapping cause the blood splinters??