The symptoms what you have given i.e., pus formation and inability to open the mouth are definitely not due to the medications what you have taken. It might be due to pericoronal infection
i.e., infection and pus formation inside the flap tissue covering your last molar tooth due to its incomplete eruption. This usually causes these symptoms. The lack of sensation in your lips might be due to the compression of your Inferior alveolar nerve
by roots of erupting last molar, which usually gets relieved by itself. So better contact an dentist
and get an x ray
done for the last tooth to confirm the diagnosis.