  We present extensive optical photometry of the afterglow of GRB~221009A. Our
data cover $0.9 - 59.9$\,days from the time of \textit{Swift} and
\textit{Fermi} GRB detections. Photometry in $rizy$-band filters was collected
primarily with Pan-STARRS and supplemented by multiple 1- to 4-meter imaging
facilities. We analyzed the Swift X-ray data of the afterglow and found a
single decline rate power-law $f(t) \propto t^{-1.556\pm0.002}$ best describes
the light curve. In addition to the high foreground Milky Way dust extinction
along this line of sight, the data favour additional extinction to consistently
model the optical to X-ray flux with optically thin synchrotron emission. We
fit the X-ray-derived power-law to the optical light curve and find good
agreement with the measured data up to $5-6$\,days. Thereafter we find a flux
excess in the $riy$ bands which peaks in the observer frame at $\sim20$\,days.
This excess shares similar light curve profiles to the type Ic broad-lined
supernovae SN~2016jca and SN~2017iuk once corrected for the GRB redshift of
$z=0.151$ and arbitrarily scaled. This may be representative of a supernova
emerging from the declining afterglow. We measure rest-frame absolute peak AB
magnitudes of $M_g=-19.8\pm0.6$ and $M_r=-19.4\pm0.3$ and $M_z=-20.1\pm0.3$. If
this is an SN component, then Bayesian modelling of the excess flux would imply
explosion parameters of $M_{\rm ej}=7.1^{+2.4}_{-1.7}$ M$_{\odot}$, $M_{\rm
Ni}=1.0^{+0.6}_{-0.4}$ M$_{\odot}$, and $v_{\rm ej}=33,900^{+5,900}_{-5,700}
kms^{-1}$, for the ejecta mass, nickel mass and ejecta velocity respectively,
inferring an explosion energy of $E_{\rm kin}\simeq 2.6-9.0\times10^{52}$ ergs.
