You can give nicknames to your Pokémon Sword and Shield, but if you decide you don't like it, then you're in luck - nicknames aren't permanent and can be changed. The only time you can't change a nickname is if you can get a Pokemon. If you are trading for a Pokémon and want it to have a different nickname, ask the person you are trading with to do so before making the trade.
How to change a Pokémon's nickname to Sword and Shield
To change a Pokémon's nickname, go to any Pokémon Center. As you enter, you will notice a counter on the left side of the room. Walk up to the counter and press A. The man behind the counter will give you some options. You can evaluate a nickname, remember a move and forget a move.
Select vote for a nickname, then choose the Pokémon whose nickname you want to change from the screen. The man will give his verdict on the nickname, usually telling you it's a cool nickname, but he'll also say you can give something better. Press "Yes", then enter the new nickname you want to use for that Pokémon.
You can do it as many times as you want, for as many Pokémon as you want, with no game costs. Just keep in mind that nicknames cannot be changed after trading, so if you trade Pokémon, make sure everyone is happy with the nicknames before completing the trade.