It's possible it's the T... even if it hasn't started changing your musculature, you may be having slight water retention. I had that for the first couple months after I started T, and I've heard it's a fairly common (and mostly innocuous) side effect. Water retention can mimic muscle pain pretty easily.
I had a decent amount of pain when I dealt with the water retention on T, but it abated pretty quickly. To my recollection, I never had any noticeable pain from muscle or bone growth. I did, however, have a good bit of pain from downstairs growth. Fortunately, it was only that was for about 4 months.
In total, I seem to recall I started feeling differently psychologically after only a few days on T, and began seeing small physical changes after about 2 weeks.