Did not listen to, but Niku is pronounced with hard K and short vowels.
Finnish is a strictly phonetic language, which means that what you see is what you say. If you see letter "I" or "U", you always pronouce them 100% the same way, regardless the word or syllable. And two times the same letter is pronounced with twice long. For example "nuMMinen" and "seläNNe" have twice as long "m" and "n" sounds than "saMi", "Niku" and "laiNe".
Pronouncing "Teemu Selänne" has been proved to be hard for English speakers, resulting often something like "Thiimu Salaani", if written in Finnish.
N is pronounciated as in "Nice", always
I is pronounciated as in "In", always
K is pronounciated as in "stucK", always
U is pronounciated as in "yoU", always
Then just put those N, I, K and U together, and you can pronounce "Niku". It is maybe easier to first say "NI" and then "KU" and then put these together. You could pretty much pronounce Finnish word "kuin" as well with these instructions, but as in "Laine", there is a catch: subsequent different vowels are kind of slided from the first vowel sound to the other, though for fun you can skip the "sliding", and still get yourself perfectly understood. If you know how to pronounce German word "ein", you know exactly what I mean with that vowel sliding.