I'm certain he feels the same way about you too... and I understand how you feel. Trust is a two way street when owning any animal.
I think the issue is the store stated he was hand tamed, if your not comfortable with him, then return him, but it is certainly not the birds fault. He has been conditioned over time to bite. Don't blame the bird, learn about him, give him a chance, he'll come around.
I have a lovebird here who bites like crazy!every time without fail.
I started clicker training him just this morning, in his cage.btw,never done this before either.
I held a sunflower seed thru the bars and he came over and bit my finger. I ignored the bite,clenching my teeth, and he took the seed...I clicked.
I waited for him to finish eating it, I offered another seed thru the bars, he came over this time, noticing the seed, bit my finger again, but took the seed a little quicker, I clicked.
the third time I offered a seed, he took the seed without biting me,I clicked!
It only took to the 3rd time for him to take the seed and not bite me.
I did this for 10 minutes, and now takes the seed thru the bars without biting my fingers.
look, it doesn't take much,baby steps.... just a little bit of your time.
I also own a Senegal who is starting to bite as well, you think cockatiels hurt, try a Senegal. I am starting to clicker train him today as well, he is hand tamed, but getting somewhat tempermental.
You will find other members on here who own the big birds, macaws,grays,cockatoos,alexandrins etc....who can really bite!!, they will offer you some advice as well, most clicker train their birds, you should look into it.