Repeating part of the salawat/durood or reading the second part again

Let's say I read the first part of darood/salwat allahumma Salli up til kamasallayta... to Innaka Hameedum Majeed. Then I continue it til allahuma baarik up til kamabarakta... To innaka Hameedum Majeed. But here, after reading the second part, I forget if I have read this second part just now or if it was the first part. So then I read the second part (allahumma baarik...kamabarakta...innaka Hameedum Majeed). But maybe now I have read it a second time. Do I need to do sajda sahu? Is salah/namaz/prayer valid?