drop class by mistake

I want to add a waitlist class at the beginning, but I need to drop it first. But I mistakenly drop another class! Now the class is closed. I immediately send an email to my professor, asking him to re-add me again. Will he give me a permission number? What should I do? Help me please!

Nobody here can help you. You need to contact me he professor and/or the Registrar.at your college.