  To clarify observational consequence of bubble nucleations in inflationary
era, we analyse dynamics of a spherical domain wall in an expanding universe.
We consider a spherical shell of the domain wall with tension $\sigma$
collapsing in a spherically-symmetric dust universe, which is initially
separated into the open Friedmann-Lema\^itre-Robertson-Walker universe inside
the shell and the Einstein-de Sitter universe outside. The domain wall shell
collapses due to the tension, and sweeps the dust fluid. The universe after the
collapse becomes inhomogeneous and is described by the Lema\^itre-Tolman-Bondi
model. We construct solutions describing this inhomogeneous universe by solving
dynamical equations obtained from Israel's junction conditions applied to this
system. We find that a black hole forms after the domain wall collapse for any
initial condition, and that the black hole mass at the moment of its formation
is universally given by $M_{\rm BH}\simeq 17 \sigma/H_{\rm hc}$, where $H_{\rm
hc}$ is the Hubble parameter at the time when the shell radius becomes equal to
the Hubble radius. We also find that the dust fluid is distributed as
$\rho\propto R^{3/2}$ near the central region after the collapse, where $R$ is
the area radius. These features would provide observable signatures of a
spherical domain wall generated in the early universe.
