What Causes Pain And Swelling At The Area Of Meth Injection?

i injected a shot of meth ice into my arm. the needle hit my vein smooth, i drew back blood, and it didn t burn when i pushed in the syringe. i felt the natural rush from the drug and everything was normal until thirty seconds passed, and it started burning and causing pain. i had all the symptoms related to cotton fever but not four days have passed and my arm is still swelled, knotted and in pain when i mess with the area where i injected the needle. what could be tha cause of this still causing me pain and should i seek medical attention?