Is this a bike from Dick's Sporting Goods or other big box discount store? You might just need to take it to a real bike shop and let them go over it. Bikes get shipped disassembled to an extent. And the big box discount stores don't have their high paid employees putting them together. They sometimes contract it out, but the pay so little per bike assembled that the person has to work at a very fast speed, so careless just happens.
Some LBS's might balk, but if they do, check with another.