Need help

Okay this is such a stupid question, I did my second shot of test cyp and I’m just curious as to why it stings when the needle goes in a bit over a half of an inch, so about a quarter is left to push in but it stings so freaking bad to push any further so I just leave it and inject, this happend my first time as well, am I hitting a vein? Or is it hitting the muscle when it starts to burn? I’m trying not to inject it into pure fat so that I can have to full affects, I am injecting on my outer quads. I’ll try to push it further but it burns so bad, I slowly inject by the way, my brain just will not let me jab the needle in my thigh so it’s easier for me to just slowly push the needle in.