as long as there is still good circulation, then your arteries havent been harmed its not life threatening. you could wait till the urgent clinics open in a few hours but until then i suggest you take it easy, get some rest, if u absolutley need a fix, muscle it in a thigh and keep you arms clean. .
DON'T IM unless you run your solution through a micron filter! Anything less selective than a micron filter will leave particles in the shot which you DO NOT want deep in your muscle tissue.
->OP: Dude, your problem is not that you're IV'ing. Your problem is you're IV'ing improperly!
Never just say 'fuck it' and deliver the shot somewhere in the subcutaneous tissue. If you do, you WILL end up with an abcess, which probably is what you've got there. I really do not get this attitude. (For me, half the pleasure of IV is seing that crimson blossom unfold, indicating a perfect register). If you don't hit the vein, pull out immediately, put on a new needle and try somewhere else. -don't dig around in the tissue and don't reuse the needle (veins are SO much easier to perforate with a fresh needle and it causes minimal damage to the vein).
-btw, same goes if it hurts when you press the plunger. Shots in the vein doesn't hurt at all, so this means that you're in the SC-tissue, should pull out immediately, change needle and try somewhere else.
From the photo it also looks as if you are injecting repeatedly through the same point of entry? If so, you shouldn't do that either. Pick a new spot each time, untill the old spots have healed completely. This will also help keep your veins healthy and long-lived.
Last but not least, FILTER PROPERLY! This is SO KEY!! Try to at least use a cotton filter, but micron filters are even better and can be bought online by the box.
Filters, needles and works in general are SO fucking cheap, that it's just a rediculous place to save money, given that these things will come in direct contact with your bloodstream.
If you could tell us how you prepare your shot, we might be able to give you some improving tips. I also HIGHLY recommend the "IV-megathread". -there's absolute gold in there.
Anyway dude, let us know how it goes, good luck and try to treat your body with a bit more respect.
Peace out!