Sometimes if you did not go deep enough into the muscle, or if you did not leave the pin in long enough, the liquid will seep back out and settle under the skin. It's no big deal, it will eventually disperse and get into the system.
I read somewhere recently that prop can actually cause this because the prop can break down the tissues. Causing inflammation in the muscle tissue. The article was stressing the importance of rotating injection areas when using compounds such as prop!
Prop causes all kinds of shit why do people even bother with it?
Prop does not cause me any problem. Everyone responds different. Keep a open mind, and learn what works best for you is the key.