I am very sorry to hear this happened.  If you can show that the infection was caused by the negligence of the tattoo shop, then you can bring a personal injury claim with the insurance carrier for the tattoo shop.  In a personal injury claim, you would be seeking compensation for the injuries you suffered as a result of their negligence.  You would be able to claim your medical bills, lost wages, compensation for your permanent scaring and pain and suffering.  Keep in mind, you will need to show that the infection was a direct result of the negligence of the tattoo shop.  If you are not able to show the tattoo shop was negligent in any manner, your claim may not go very far.  I would suggest you contact a personal injury attorney in your area and seek a consultation.  He or she will be able to hear all of the facts of your case and give you a fully informed opinion as to what your legal options are at this point.  Most personal injury attorneys offer free consultations and work on a contingency fee, meaning you do not pay any attorney fees until your case is settled or resolved.  Good luck to you.