I AM NOT A MEDICAL PROFESSIONAL, but I've delayed one day so I could do my shot on a different day of the week, and I have never had any problems. I've also done a shot a day early for the same reason. I went to a weekly shot because I was feeling a significant mood drop a couple of days before each biweekly shot.
If you got the shot tomorrow, how many days early would that be? If it's only a couple of days, maybe you can have a shot early and then do the next one in exactly two weeks, as usual. The T in your system starts to decrease before the two weeks are out, you know. Hudson's FTM Guide has reliable info about T levels and troughing--you might look it up. Or just call your doctor and ask.