It couldn't hurt to put a hot compress on it, just wet a towel or cloth with hot water (not searing hot) and apply it to the area with firm pressure.
Honestly man, it sounds like you didn't miss much at all. I have done this a few times with meth and it's always been fine. This, however, does not mean there's not a chance that something will go awry with your small miss - particularly working with injecting pills, there's always a chance of abcesses and such.
Keep an eye on it. If it becomes tender, red, more raised or grows in size at all go to the doc and get it checked out as it could be an abcess, the consequences of which people have lost limbs to before (and if not a limb loss, have attained some hideous looking scarring and injury).
STILL, doesn't sound like your is much to stress over, so don't beat yourself up over it.
I wouldn't recommend releasing your tourniquet halfway through a shot again. Push needle in, register, release tourniquet, re-register and inject. Is a tourniquet 100% necessary for you to find your veins? I've always found them cumbersome. Try doing some push-ups/bicep curls or taking a hot shower before doing your shot to make your veins pop out.