I had a blood test and they couldn't get any blood for ages they did eventually but now my arm is very achey and sore should i be concerned about anything?

If your arm otherwise works normally, I would not be too concerned. Poking around in the area likely injured tissues and produced unseen local bleeding that would hurt/irritate until the body self healed. Applying moist heat to the area can speed the recovery process by improving blood flow carrying healing factors. Heat can produce a transient increase in the pain involved but may be worth it