Thank you for your inquiry and thank you for your patience on such a time sensitive matter. From what we gather from the question, you were asking about the possibility of HIV transmission in the event that you scratched yourself with the presence of blood product under your nails.
From the information given, this scenario is determined to be No Risk (HIV transmission is not possible in the given scenario). Small scratches, especially with blood that has been exposed to environmental surfaces or oxygen are of No Risk to you when it comes to HIV transmission. HIV outside of the body or drying HIV positive fluid undergoes a rapid reduction in concentration when exposed to the environment (1). For this reason, under the circumstances that you have described, there would have been no opportunity for HIV transmission to occur.
HIV transmission mainly occurs from person to person, and only under certain extenuating circumstances (such as needle sharing) is it able to transmit from environment to person.
Further, unless you had accidentally injured yourself with a tool or needle that was previously used on another, or engaged in any other High Risk activity (condomless sex/breast feeding), there is no need to seek out PEP (Post-Exposure Prophylaxis) for immediate treatment.
Recommendation: No need for HIV screening and/or PEP for the scenario provided. Please refer to your health care provider for additional health related questions.
All the best,
AIDS Vancouver Online/Helpline, Cody