You won't need to do anything to stunt its growth, the pot will do that for you. The height you mention is only attained by plants growing outdoors in open ground, and it won't reach anything like that in a pot. I have to say the plant already looks too large for the pot its in,so you should really pot up into something larger. But remember, a plant stunted by lack of room at the roots is unlikely to flower well, so you should aim to eventually have it in the largest possible pot you can find that you can still carry as it grows on. Give it the sunniest position you're able to find for it if its indoors all the time. With regard to bonsai,this is not a particularly good subject for that sort of treatment - it does not like being constantly pruned or cut back, but there's nothing stopping you trying if you want to give it a go.
Note though, that the fragrance from the flowers can irritate the airways of asthma sufferers, especially if it flowers indoors. All parts of the plant are toxic, the seeds/fruits being more toxic than the leaves. The smoke from any part of this plant, if burnt, should not be inhaled. To be honest, the scent from this plant when in flower is so strong, you'd probably have to move house till it finished, but maybe some people don't notice it so much as others. Some warnings in the two links below
http://entheology.com/plants/cestrum-nocturnum-night-blooming-jessamine/
http://www.mediterraneangardensociety.org/poison.html
