I don't know for sure but if it's a girl, I think you take the first part of the name and add uška or íčka or something of that nature. My step daughter is Bara and sometimes her dad calls her Baruška and her daughter is Eva and sometimes they call her Evíčka. That's all I got for you. Sorry. More people will help you though, I'm sure of it.
Give wider context 8) "Ty můj pitomečku malej!" In Czech for little somobody/something we use special endings with the word pytel / pytlíček Eva / Evička Jaroslav / Jaroušek voda / vodička máma / maminka / mamulinka slunce / slunko / sluníčko brouk / brouček / broučínek kotě / koťátko some ot the endings masculine: -ek, eček, íček feminine: -ka, -ečka, -ička, -uška neutrum: -ečko, -átko, -íčko etc...
Are you actually asking how to use a diminutive form of someone's name, or how to say a generic "little one" My boyfriend used to call me "mrnous" (with a hook above 'n") which meant "little one" or you can use "mala" or "malicka" or "malinka" You can add "moje" if you want to say "my little one" (moje mala). (I am sure someone will print this over with all the diactrical marks)
That one is really odd when translated into English "my little crumb" :lol: But at least a good thing about this one is that you can use it for a male (though hardly to an adult man, since they may feel "emasculated" :wink: ), or a woman.
For a small child, I've also heard prcek, which as close as I can find roughly translates to "little squirt."