What Could Have Caused Unexplained Bleeding From A Pin Sized Hole On Shin?

I am on warafin. Today getting out of the shower....I did not shave or bump myself...while I was drying off I looked down and blood was streaming from a small pin size hole on my shin near my ankle. My husband applied preassure and I lifted my leg. When I stood up and showered the blood off my leg it started bleeding again. Pressure was applied, raised my leg and wrapped my leg with gauze bandages.

No bleeding for several hours now. What would have caused the bleeding?