You're probably injecting wrong, and should not be participating in the use of anabolic steroids if you are in too much pain from 2x/week injections. Not trying to be a jerk here, but just giving you a reality check.
Medial Deltoid - R & L
Vastus Lateralis - R & L
Dorsal Gluteal - R & L
There's 6 easily accessible sites right there, which allows you to not inject in the same spot until 14+ days later. You should be able to inject 3x a week, and if you wanted to do 4x, you could add something as simple as your R and L pectoralis major.
Do not take tren with an acetate ester once a week. Even if it was enanthate, it would probably be better to use it twice a week for stabilized blood levels.
I highly suggest you do 3 injections a week if there is acetate ester. If you don't want to do this, then switch to only tren enanthate, and then you can do 2x a week no problem.
To be honest, it scares me that you're using tren and are talking about "running out of places to pin" and being "too sore" from your extremely small # of cc's you're running on an anabolic steroid cycle. From the impression I'm getting, I have a feeling others would agree you should not be touching tren. I would stick to test and probably just run 500-750 a week in 1-2 injections, and once you become more experienced - consider other compounds, especially...something like tren.
You may not like my advice, but hey...I tried.
PS: If you use a 25gauge, 5/8th inch or a 23-25 gauge 1 inch , and inject slowly @ 0.5cc at a time followed by a 10 second pause, and then continue the rest, you should not be getting sore unless whoever is making your compounds is using garbage as solvents.
Good luck!