The only thing you can get is Hep B as the HIV and especially AIDS virus' dies when it outside the warmth of the human body. I used t worry when I get covered in blood at work but now see it as part of the fun, although there is a risk there as the blood is normally warm, hence plasters on any cuts and double bagged "surgeons gloves".
My mum stood on a hypodermic needle years ago, that really shook her up though.
Andy