You have nitrated ortho-bromotoluene. Since this compound has two ortho/para directing groups in a conflicting orientation (ortho to each other), a complex mixture of products will result (formulas shown to the right). Proceeding to the desired product from this point is not feasible. Note that the location of the bromine substituent relative to the methyl group (destined to become the carboxyl group) is not the desired para relationship.