ANSWER:

Your prayer is valid however you should have made sujood as sahu after salam and made another set of salam after that.

Sujood As Sahu (Prostrations of Forgetfulness)

I didn’t remember that I offered sajda in my prayer then I add the rakah in my prayer as first one in which I didn’t remember one sajda become void. After completing my dua in last tashahud I offered sajda sahu and then offered salam. Is my salah valid or not?