in fact, by the why the test kits are designed, it would be impossible to use the same one twice. Further, perhaps it will help you to know that
in the US and
Europe in the past 20 years, probably there has not been a single case of HIV infection occurring as a result of drawing blood, or by use of a finger-stick lancet.
So you can absolutely rely on your negative test result and should not be at all worried about being infected during the testing process. There's simply no chance of it.