It happens all the time. You buy a ticket, then something happens to change your arrangements for the return trip. So change your return.

If you can't change your ticketed return, buy a new one. Maybe you'll have to forfeit the return ticket you already bought. That's OK if it ends up costing less.

Fly the outbound first, then either cancel the return, or just don't show up for it (and they will cancel it when you no-show). No big deal.