Give it time make a fuss of the bird but dont overwhelm it. Imagine how you would feel in a strange environment. Would you settle straight away.

You need a month to three months. Feed the bird some millet from your hand. Yes bites can hurt they can break the skin and draw blood and they will if very scared. However do not worry. They are social birds and desire interaction.

None of mine like their heads petted Ive had them now for 13 years.

Some tiels will allow it though head petting.

i have 2 tame onze evan when i am petting it it allways trys to bite but it dose not hurt they bite because they just think its a way of playing dont worry she or he is fine also the bird is very tame if you only got it yesterday as mine took me 3 weeks before i could evan put my hand in the cage

You need to develop a bond with yourr birdy. It doesnt even know who you are yet. It will get used to you

It just got here yesterday and i can pet its head. but then it flinches so it can bite me. i have been bit but it doesnt really hurt
do you think he needs more time to adust?