If your the part where the tattoo is swollen for almost 4 days, and there is a pain it means your tattoo is infected. My brother have is first tattoo and it get infected. But to make sure, ask and follow what the tattoo Artist would tell you on how to take care of your new tattoo.
Red, inflammed, tender to the touch, warm, purlent discharge (ewww!). Time to see your primary care doctor for some antibiotics. Keep the site clean, wash with hydrogen peroxide and water, apply antibiotic ointment and a clean dressing.