My bad...... But I hardly ever washed my hands before finger-pricking (back in those days before the Libre)
Only if really having had them deep into nasty obviously and still visible dirty stuff would I care to wash my hands before testing.
If just running a decent personal hygiene you wouldn't need to at all.
Your bg test result will not be impacted by it. The only real important thing is that the fingertip is dry from any liquid substance before you start. Let me expand a bit on that and why other dirt doesn't really matter much:
Though we see a ton of different test strip brands, with difference sizes, shapes and prices - They all function the same way both mechanically and bio-electro chemically. (yep, they are good at marketing, those billion dollar profit companies...)
A test strip consist of a multitude of distinct material layers that each serves its own purpose. We can all see and experience the top layer, which is the sponge that soaks up your blood sample droplet. Next it runs through a couple of filter layers (here your garden dirt wont pass

). And then it comes into the reaction area of the stick. It is composed of 3 components: the glucose oxidase enzyme that reacts with the blood glucose (and it can only react with glucose), a catalyzer chemical that speeds the electrons along the test strip electric circuit, which enables an accurate reading can occur before the reaction fades out, and then also a chemical compound that preserves the enzyme and mediator chemicals. Below this you have the gold and palladium coated circuit that transfer the reaction electrons to the meter for analysis. And the meter's computer chip converts the current into a numerical reading for you to read. So just keep your finger tips in reasonable condition, make sure they are dry and you are good to go!