Yes. He has to draw back on the plunger. You do not want to put the oil into a vein, which could lead to your heart and kill you. Pull back slightly on plunger. If no blood, then inject slowly. If blood, pull the needle slightly out and pull back again. If giving in glutes, you should not hit to many veins or nerves. Stay away from middle buttocks as that is were the sciatic nerve runs.
PS: Karma is always welcome and repaid!