Your cockatiel is just a baby and just weaned so you offering food by hand is kind of like his parents feeding him be careful you don't set yourself up in a fight for your little one to be independent later rather than sooner by doing too much hand feeding.
Try doing it this way he gets to try it in your hand and then put it down in front of him don't continue to hold it. Ok this is going to sound right weird ….. you have a nibble of something and let him try and then gently place it in front of him lower your head down as if you peering at it to have a feed and make yummy noises. Play with his food in a bowl and find out what is the absolute tastiest thing in the world that he can't resist and do it with that.
I had to teach an older bird (Henni) about eating fresh fruit and veggies again she wouldn't touch them unless I held it and then I migrated her into having food at the same time as me … what was on my plate was on her plate …. yes I resorted to plates and a place for her at the table!! Sometimes you just have to think outside the box and try whatever you can to get them to have a go
and yes that is a cup of juice Henni has! This picture was taken a long time ago of us eating out in the garden that's her half of the patio table lol. But for her it eventually worked and after that she was ramraiding the fruit bowl and generally grabbing anything and everything she could get her beak on!
I also had to wean Junior a baby tiel who I hand reared from the day she hatched which for me was a whole new ball game too! I did that by pretending to eat the seed and then sharing and putting my fingers in a tiny seed dish how on earth she learned to hull the seed is beyond me must have been instinctive is all I can think thank heavens!
Was so proud of Junior learning I just about burst in to tears
@sunnyring is a breeder and keeps tiels and rears them and very a very knowledgeable lady hopefully she will pop on and give you some tips
My methods can be a tad unorthodox at times as most of my birds are not exactly what can be termed hmmm errr totally normal (rather like me lol) but we get where we're going and that's what counts adapting things to the bird if needed