To figure out what the boy’s name is, you’ll need to figure out what the tattoos could mean and how they relate to the boy’s name.

The number 3 is over one of the vertebra of the boy’s spine. 

Each number is over a part of the body. You’ll need to take the first letter of each body part to spell a word. 

Put the number into the lock. The first number will be zero. 

The number three is over one of the vertebra in the boy’s spine giving you “V”. Starting from one you get “S”, then two and “E”, then three and “V”, four and “E”, five and “N”, 6 and “T”, 7 and “E”, 8 and “E”, 9 and “N”. Giving you the boy’s name, “Seventeen”