Pinterest is very diverse niche friendly. Unless your target group is entirely different, we do not recommend creating a new account as you will have to start from zero again.
If you already have traction stick to the same account and update your boards accordingly. We never recommend deleting boards either. If you feel you are not able to update a certain board, you can archive it instead. You don’t need to update all your boards on a regular basis as long as you create content your audience wants.