You have simply put more holes in your penis, thus more ways for germs to enter. Have clean hands when handling your nether parts, and always use a condom (or two - your piercing can rip a condom).
Hi if you are getting a Tat or piercing you must let it heal before attempting any sex , always keep the area clean what ever you get done , Try and see the Tattooist's work before you get your Art done , take care