Apple watch series 3 unlocking

Hey there, my Apple Watch series 3 is linked to my old phone that is completely dead and I do not want to spend money to get it repaired. My son played with my Apple Watch 3 and locked it, so now I cannot link it to my new phone. How do I unlock it? it does not allow me the option to reset it without entering the pin code, but because it is locked I am not given the option to enter the pin...