  The growing evidence of gravitational waves from binary black hole mergers
has renewed the interest in study of primordial black holes (PBH). Here we
study a mechanism for the formation of PBH from collapse of pseudo-topological
domain walls which form out of equilibrium during inflation and then collapse
post inflation. We apply the study to domain wall formation due to $D$-parity
embedded in a supersymmetric grand unified theory (GUT) based on $SO(10)$ and
compare the abundance of resulting PBH with the existing constraints. Thus the
macroscopic relics can then be used to constrain or rule out a GUT, or demand a
refinement of the theory of PBH formation in this class of GUTs.
