yes you can open the valve to release the fluids and then try to push the piston in , but then i tell you it would be hell for you to push it back in just like that . u either need a special brake tool or use a player to twist the piston inwards . actually no need to bleed the brakes , you can run with your current fluid , the fluid has notting to do with your brake lock , its obvious that your piston is jutting out from where it suppose to be align .
bad guy , yes you can use the screw driver way , but then it would be harder , cause the piston is not going in straight , it will be abit crooked , that method is old skool / faster runner method , which people don't practice anymore . cause long term results , will scratch the wall .