You might.

If you fly a routing that isn't valid and you know it, then you have intentionally breached the contract of carriage. UA can recover whatever it is entitled to under said contract.

I would stick to valid flight routings to keep from getting in any trouble. It looks like you changed your reservation without revalidating the ticket. You may end up showing up for a flight on which you have a confirmed seat but no valid ticket and be given the option of paying the correct fare or not flying.