Pain & swelling the next day is not something I've had, and I'd question the quality of what you got. If you did your research, and are injecting correctly, you shouldn't have more than a mild soreness the next day, if that at all. Swelling means something might not be right. If you're not getting the needle all the way into the muscle, that would cause a subcutaneous blob of oil, and that could explain it. Basically, take a pinch of skin & fat, and see how thick the pinch is. You want the needle to go 3/4" deeper than the pinch. (So if you pinch 1 inch thick, that means roughly 1/2" skin tissue and fat pad to go through, plus 3/4" into the muscle = a 1.25 to 1.5" needle. If you have ultra-low body fat, you can get away with a 1" needle, but it's better to inject a bit deep than a bit shallow, in my experience. TOO deep is bad also, as you will REALLY feel it if you hit the bone, the sciatic nerve (OUCH!!!!!!!), or of course if you hit a deep artery it can cause a major deep muscle hematoma which can also in some cases, lead to a life-threatening embolism. So if you're very lean, you need to be careful. Basically imagine the muscle as a ball (no matter glute, quad, or delt), and aim for the very middle of the part of the muscle suitable for injecting (good info on Internet on those sites).
Charles