It is very normal for any animal to bleed when they get an injection, don't worry about it. It simply means that the needle went through a capillary or small vein.
I just had my vet out to geld a horse and a couple of llamas and while the llamas were down, we trimmed their feet, gave them their monthly shot of Ivermectin, and a tetnus shot since they were being cut, and even he had one bleed a little at the injection site.
What you do need to make sure to do is to pull back on the syringe after you insert it to make sure that you aren't putting the Ivermectin into the vein--as DonnaBelle mentioned, this shot is to be SubQ, not IV. When you pull back on the syringe after inserting the needle you want to make sure that you don't see blood.
Hope that helps--and don't worry, giving injections will soon become as routine as any other animal chore. It really is no big deal.
Good luck!
Therese