It is very common if you're injecting into the quads. I've never had that issue with glutes (by far preferable, all around). There are many more veins in the legs than the gluteal area (nerves also). When you bleed like that, it means you've passed directly through one. But the T will, usually, have been deposited lower than that point (muscles only have capillary, or very tiny, veins. You won't see any blood coming up from them). As long as you're not getting blood in the barrel, you're alright (and your T, of course, will still work as ever).
Even though they now say you don't have to aspirate (pull back a bit when you're in), I do and will always do so. Better safe than sorry. Oil does not, ever, belong in the vascular system. Most other IM substances are not suspeneded in oil... which makes them a non-issue for this, however that is NOT true of T (which is oil-based).
Everybody injecting IM in the quads SHOULD still aspirate, given that there are so many more veins there, than the recommended injection site (glutes). Those doing SubQ, needn't bother (so small of a dose and so shallow there won't be any risk of hitting a vessel).