How Is HIV Transmitted?

Question: about a year ago I was working in a haematology laboratory and processed a bone marrow sample from a patient who was HIV positive without gloves on. the sample was collected the day before and stored at 4 degrees Celsius overnight. I am worried that I got some on my fingers. I do bite my nails (my nails were checked for any open cuts and the health care professional didn't believe it necessary to start me on PEP). I didn't mention to them that I may have bitten my nails after the exposure (I do not remember). since then I have had three negative home tests for HIV. I think the first one, which was the rapid antibody test, was taken to early (about 3-4 weeks after). I did antigen tests at home, which were sent away to a lab, about 3 months and about 6 months after as well, which were both negative also. my concern is that I may have got blood in my mouth if I bit my nails maybe 1 or 2 minutes after (I don't remember). I wonder if you think I should be worried? thanks

Thank you. however as it was a while ago I do not remember if there was a cut or ulcer in my mouth. I know occasionally my gums bleed when i'm cleaning my teeth. for it to have occurred this way the blood would have XXXXXXX on my finger for a short time. if that were to have occurred should I be worried?