ummm.. i haven't actually heard that one.. purple huh..
If you still have mobility in your arm and there isn't pain i'd say you're fine, unless it gets worse tomorrow then get it checked out.
check out the "safe guide to injecting", umm no link off the top of my head.
you know i'll bet its because you have an iron deficiency and you just bruise terribly easy.
veins dont last forever man, thats a lot of times to poke yourself. i used to do it but when you start to see the veins fade its high time to really slow down.
having poor blood flow (collapsed veins) can easily take 15-20 years off your life..