What Causes Rising Pimple After Having Tattoo On Lower Hip/stomach?

I got a tattoo on my left lower hip/stomach region on December the 19th. A few days ago I noticed a rising pimple on a region of my tattoo and it has developed a white head, today I noticed a red, swollen, inflammed streak leading from my thigh area up to the area of the pimple and a swollen knot under my skin ( lymph node ? ) right outside the area of the inflamed streak. I'm concerned , I don't know if I should go to the doctor or what.