I don't speak Finnish. But I did once hear David Axmark pronounce My's name, and to my ear it sounded like "Mih" - an "M" followed by a short vowel similar to the vowel in "bit". In other words, My's name is the same as Mitt Romney's first name, just without the "t" at the end.
You might want IPA [ɪ]. (But another comment in this thread suggested [y], a sound that English doesn't have, and which is close in several ways to English [i] in "me" or [ɪ] in "bit".)
