hello and welcome to HCM forum,
i would like to inform you,not to panic,it is one of the complications of local anesthesia
you have not explained whether the swelling is red or blue in color, I assume it is bluish in color.
kindly apply cold
compresses on the affected cheek atleast 3-4 times a day.
if the swelling is painful, you can take oral antihistamines as well.
swelling will take 3-4 days to disappear completely.
in case the swelling does not subside,kindly visit your dentist
i wish you good health.