  We study the regularity of the viscosity solution to the fully nonlinear
parabolic thin obstacle problem. In particular, we prove that the solution is
local $H^{1+\alpha}$ on each side of the smooth obstacle, for some small
$\alpha>0.$ Following the method which was first introduced for the harmonic
case by Caffarelli in 1979, we extend the results of Fern\'{a}ndez-Real (2016)
who treated the fully nonlinear elliptic case. Our results also extend those of
Chatzigeorgiou (2019) in two ways. First, we do not assume solutions nor
operators to be symmetric. Second, our estimates are local, in the sense that
do not rely on the boundary data.
