If you hit a vein you will probably develop a haematoma, basically a bruise. You inject into muscle for slow absorption of the T, you are highly unlikely to inject into a vein unless you deliberately try. You are far more likely to nick one and see the blood release. If you did inject T directly into a vein it would be cleared quite quickly, rather than being absorbed as you want it to be. Unless you are allergic to T or the carrier it is in there should be no effects, and if you are allergic you would know it by now anyway from the IM injections. Which is one reason the initial injections were probably given in some sort of medical setting, so if you had a reaction they could retrieve you.
BTW there is quite a lot of mythology about injecting into veins, to induce a myocardial infarction in a healthy normal adult person, you need to put about 50mls of air into a vein. That takes a bit of doing. That does not in anyway mean to experiment, or get careless, and the calculations are based on the big rat model. That is if this does that to a rat then someone ten times bigger than the rat will have suffer this affect.