Alot of variables can be the reason for Pip . Ill try to explain a few . The most common among new users is user error. Also wiggling the needle from nerves while injecting , it falls under user error . In some cases the bottle will start to crystalize and yea that would hurt . Heating it up and that will fix it. Long but not least , Alot of compunds itself cause PIP , typically short esters , They have been known to have some bite like dhb ,primo, test prop, test base .You can get pip on higher mg compounds like T400 . The list can go on . I assume with you that your new to injections and that's what happend with virgin muscle ...It won't last long . Typically a day while it breaks down into your body... Sometimes ill give myself pip and I know it was my own fault for pushing the oil in way to quick ... But Ive done hundreds of Good shots successful .. very seldom its the labs fault but most reputable labs will help you out if is the batch ..