OkAy I Am A 25 Year Old Girl, I Injected

OkAy I am a 25 year old girl, I injected heroin into my wrist the blood drew up but when I go finished I got a severe psi. In the palm of my hand now my wrist is swollen but my huge concern is that my pointer n middle finger are really swollen pure white and cold what is going on and what should I do? I'm totally FREAKING OUT an would appreciate your advice.