ANSWER - Contrary to popular depictions in fiction - the presence of a spirit
in the home presents very little threat to the inhabitants. Most people occupying a house with a place spirit in residence are unaware even that they are sharing their home. The impact of a spirit inhabitant is pretty low and especially in homes without children or animals present spirits and humans can live quite happily side by side having very little to do with one another.
That said, part of the reason that spirits tend to be benign toward the mortals they share a house with is due to the fact that unobservance//indifference causes the spirit very little difficulty. Repeated forced attempts to interact with a spirit may well change its attitude toward those it house shares with. Botched exorcisms, relentless ouija board sessions and a general lack of respect for the privacy of the spirit may either encourage it to move somewhere else or turn it antagonistic toward its housemates.
If a spirit hasn't made an effort to draw attention to its presence then likely it has a valid reason for not choosing to do so and it may well not appreciate this distance being breached by even the most well intentioned of communications.
I do not think there is anything wrong with indicating a willingness to communicate and in my opinion this is not likely to put you in a position of danger. What I do suggest though is that once you have initiated this contact attempt you leave any further interaction to the spirit and do not persist or attempt to press the spirit into a response. I would do something very simple - a clearly voiced respectful address to the room in which you have been advised the spirit frequents. Introduce yourself, thank the spirit for its presence and state that you would be interested in making further contact. Leave it there - if it wants to communicate you will know soon enough. If it doesn't - no harm done.
I wouldn't be alarmed that you happen to have a spirit in your home. They are far more common than most people think. What is not so common is the ability to perceive them. So in this case it is actually your nephew and not the spirit who is the interesting factor in your story. I'm presuming he is young - children do seem to be much better at seeing beyond the veil than adults who have learned scepticism and become entrenched in the mundane. Don't dwell on his sighting - children are not naturally frightened of spirits but can easily become frightened if they pick up and sense that response in adults. Treat the child similarly to the spirit in fact - make it clear the doors of communication are open and then leave it for both the child and/or the spirit to come to you if they want to.
And as I say, don't be frightened, there is no reason at all to assume the spirit means you any harm and I'm sure from what you say it doesn't.