Handle it handle it handle it handle it. Nile monitors, aside from crocodile monitors, are the biggest nastiest lizards you can own and they aren't the smartest of the large monitors either so it's hard to know when they are going to act up. If I was you I would take it back and exchange it for a water monitor - less aggressive, more intelligent, much more likely to tame down like a dog. I know people that trust their adult 7' water monitors with their small children - they would NEVER let even a medium sized child around their nile monitors.
They can be great pets but be prepared to give them a ton of space (8x8x8 minimum), feed them a ton of food, and never turn your back on them.
Awe, cute little water monitor
Better yet get an akie - Varanus acantharus. These are dwarf monitors with a personality like a big monitor
And never hand feed - always tong feed.