  We present a comprehensive study of the vortex pinning and dynamics in a
high-quality FeSe single crystal, which is free from doping introduced
inhomogeneities and charged quasi-particle-scattering because of its innate
superconductivity. Critical current density, $J_c$, is found to be almost
isotropic, and reaches a value $\sim$ 3 $\times$ 10$^4$ A/cm$^2$ at 2 K
(self-field) for both $H$ $\|$ $c$ and $ab$. The normalized magnetic relaxation
rate $S$ (= $\mid$dln$M$/dln$t$$\mid$) shows a temperature insensitive plateau
behavior in the intermediate temperature range with a relatively high creep
rate ($S$ $\sim$ 0.02 under zero field), which is interpreted in the framework
of the collective creep theory. A crossover from the elastic to plastic creep
is observed, while the fish-tail effect is absent for both $H$ $\|$ $c$ and
$ab$. Based on this observation, the origin of the fish-tail effect is also
discussed. Combining the results of $J_c$ and $S$, vortex motion in FeSe single
crystal is found to be dominated by sparse strong point-like pinning from
nm-sized defects or imperfections. The weak collective pinning is also observed
and proved in the form of large bundles. Besides, the vortex phase diagram of
FeSe is also constructed and discussed.
