Ok there are a number of theory’s in regards to PIP.
One, it’s the solvents used like benzyl alcohol (ba), benzyl benzoate (bb), and ethyl oleate (eo). Depending on how much the lab used then the bb could be causing the issue but really it would have to be pretty high Concentration.
The second theory is the solution crashes once injected either from not enough solvents or when they made it they didn’t heat it properly to melt the hormone thoroughly. Is your product from an UGL? Chances are that it is even if it looks like Bayer or fizer made it, it’s probably a name brand knock off. That’s ok most of our stuff is the concern is weather you got your hormone or not and if they made it correctly.
So what can you do to reduce this PIP for the future, there is two things I know of. One try heating the oil. If it is in a bottle then put a small amount of water in a pan and put it on the stove at like 2-3. Put a venting needle into the vile so when it heats up the expanding air can excape. If it is test enanthate in the vile then that stuff should be good and melted at like 100 degrees Fahrenheit so get it to like 120-130 and your good.
Second thing you can try is dilute the oil. Get some filtered sterile gso or cso off the internet. Remember it needs to be filtered and sterile. Then you just fill half the cc with just the oil and half cc of the steroid, shake and roll it around to mix it then inject.
A lot of guys randomly have just some strange out of character reaction to either one batch or some new UGL product. Most of them stick to very similar recipes because they have figured out how to make an acceptable product for the cheapest way possible.
The last thing is maybe it was just fresh muscle or you injected to fast. Remember a new muscle will hurt the first few times and no matter if it is a new or old muscle go slow, like take a minute to push in a CC. It gives it time to discapate rather than tear the muscle.
As far as it hurting for a while I would think that leans towards the hormone still being in Crystal form inside the muscle. Little tiny crystal rocks tearing at the fiber. That slows down the absorbing and effects the half life. Try the heating method first.