Hi there ~
I understand your concerns. Shooting up heroin
is associated with localized inflammation of the vein or the cutaneous tissue if improperly used and may result in infection. I believe that the lump on your skin is due to infection that is getting worse and it could be an abscess
. I also think that it is impinging on the nerve
to the extent that your fingers are getting numb. I believe that the color also indicates in this direction. A consultation with a local doctor to have the abscess drained and having an antibiotic that will help heal the infection is what you need to take care of the issue. You may use over the counter anti inflammatory and analgesic
medications. I do not think you can be treated at home and you most definitely need to visit with a doctor.
I hope this helps. Take care and have a lovely day!