What Are The Side Effects Of Warfarin?

Hi, thank you for being here. I'm on warfarin, 51, post-menopause. One of my nipples turned dark and on pressure, expressed black blood; wait a moment, it refilled, expressed again, about seven times for probably less than an eighth of a teaspoon. The first time this happened, the final tiny bit was infection-green, not black -- but there's no heat or pain I'd associate with infection. This has happened three times in three weeks, but the green only appeared once. What's up?