I forgot to mention that i did ghusl after doing ghusl

Today I did ghusl to rid of janabat. I kept niyyah and did ghusl. However after I finished ghusl I forgot to declare that I have finished ghusl and say the dua after ghusl, as my mind was occupied with other thoughts. I remembered about it only a some time later. So is my ghusl valid ? Should I make ghusl again ? What about the prayers done in such a state? If ghusl is invalid should it be redone (although I was ignorant of the matter ) ?