Friend and I are both experiencing the same symptom. It's been a while, but I don't remember this happening on my previous cycle (couple years ago).
Inject once weekly into the glute (only 300 mg of test e), alternating sides each week, and it's a bit sore the day after maybe, which goes away, but about the 2-3 day after mark, we're developing a small knot an inch or two just above and to the side of our tailbone, on whichever side we injected that week. It's quite sore, and you can't see it very well, but you can obviously feel it under the skin. It feels hard, and maybe half the size of a golfball. Eventually it goes away, usually just in time for next week's shot.
It is not, I repeat, not at the actual injection site. It's confusing me - it's almost like the oil migrates over there and then stays put as it slowly absorbs or something. My personal (and completely unfounded) theory is that it's an inflamed lymph node or something). Both of us got the same batch of gear, presumably.
Made sure we have been as sterile as possible, two needles per shot, alcohol swabs, letting it dry, etc. Still getting it. It's not debilitating or anything, but it's annoying, particularly because I don't know what's causing it.
Anyone got ideas?