What can you legally do when the person who hit you insurance company will not pay for the accident because their insured is denying fault but he was cited at the scene?

If you have insurance call YOUR insurance and they will pay for your damages and then they will subrogate (meaning they will go after the other persons insurance for reimbursement) If the other person has been cited then they are clearly At Fault. Nobody can deny that, make sure you contact the police department for a copy of the police report as well.