Without knowing what it was printed with printer or resin; it's hard to tell you what to do.
From the lines in the part, this was likely printed on a low-cost resin printer.
However, there should not be any uncured resin in a part that is shipped for sale. All resin must be fully cured, or you may get a nasty rash by touching uncured resin. Not a good look.
The UV pen light will likely cure the uncured resin, assuming that the wavelength of the light matches closely with the laser or UV light that formed the piece.
