Bike crashed on me, there was blood all over my arm. and i was bleeding myself as well on my own wounds. the blood of biker+me contacted! hiv possible?

Worry: First - heal from these injuries. If you known that the biker is hiv+, then yes, there is a risk and it is important to be tested and start recommended treatments. If the biker is a stranger but now you have contact information - you could ask for their HIV status and relax if they have a negative test result. If it is just an unknown - go ahead and test to avoid rumination and worry. Best!

Very unlikely: This is a slightly different story from the way i first understood it. Hiv is hard to transmit, but there is one account of the easier-to-transmit hepatitis c virus passing during a bloody fistfight. It is far-fetched, but you'll want to decide with your physician -- if it's within the window of opportunity -- whether to do prophylaxis. Do you know the other guy so he can get checked first?