As we no longer have modified live rabies vaccine the vaccine you used is most likely a killed virus vaccine. This is much safer. The likelihood of contracting rabies from a serious exposure like splash back in the eyes is most likely not possible.
You may experience some irritation of your eyes from the vaccine and the preservatives in the liquid.
I think you are not in an emergency situation but I do recommend you take the vial of vaccine with you to your doctor tomorrow and discuss any secondary side effects.
This syringe blow back is caused by not getting the needle properly seated on the syringe and the position of the Sub Q needle was most likely not correct.
This is why the law requires veterinarians to administer rabies vaccine as it is a dangerous disease and vaccines must be given properly and safely.
Good for you in making sure you at least try to vet vaccine in him. Needles do loosen up from the syringe, but also if the needle is in the skin layers or up against a hard surface that helps to create the back pressure and will sometimes blow off the needle. If he got most of the dose you are probably okay, if not, I would revaccinate him and make sure your vet shows you a sure fire way to give a sub q vaccine.
Good luck
Thank you so much.
Yes it is a law here that a dog has to have the vaccine adminstered by a veterinarian but this dog is pretty wild and will not let anyone touch him but me so I make sure he has his shots. The vet sold me the vaccine already filled in the syringe. I should have made sure it was on there tight.