Yep boyz sharps can be seriously detrimental to yer health....
Critically make sure it's an uber new, sterile and sharp syringe I prefer those made by B&D....and totally air bubble, air speckles free...
Try to rotate sites as much as possible to avoid over tissue damage/scarring from regular same place injections....
Make mental notes of the bad places, where uber bleeds kicked off, and try to avoid those in future...
If in doubt don't.... and if you have a savvy SO that knows (exactly) what they're doing its oft easier if they do it for you...defo if they be a nurse or medically trained...
Happy skin hunting guyz...lol
Auntie C