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Motivated by the recent release of new results from five different pulsartiming array (PTA) experiments claiming to have found compelling evidence forprimordial gravitational waves (GW) at nano-Hz frequencies, we study theconsequences for two popular beyond the Standard Model (SM) frameworks, wheresuch nano-Hz GW can arise due to annihilating domain walls (DW). Minimalframework of Dirac leptogenesis, as well as left-right symmetric model (LRSM)can lead to formation of DW due to spontaneous breaking of $Z_2$ symmetry.Considering the NANOGrav 15 yr data, we show that the scale of Diracleptogenesis should be above $10^7$ GeV for conservative choices of DiracYukawa couplings with fine-tuning at the level of the SM. The scale of {\itminimal} LRSM is found to be more constrained $M_{\rm LR} \sim 10^6$ GeV inorder to fit the NANOGrav 15 yr data. On the other hand, the {\it non-minimal}LRSM can be compatible with the NANOGrav data for $10^2 \, {\rm TeV} \lesssimM_{\rm LR} \lesssim 10^3$ TeV but with the corresponding $B-L$ breaking scaleviolating collider bounds.

Scale of Dirac leptogenesis and left-right symmetry in the light of recent PTA results