Hole at the back of my inner cheek

[W1ll1am]

Hello! I have this hole at the back of my inner cheek that has pus inside. It is really uncomfortable and sometime my teeth and jaw near that hole hurts. Could someone please tell me what it is and if there is any treatment. Thank you so much
(The first picture was taken 2 days ago and the second one today!)

 

[MattKW]

Can't be sure. Do you have an upper wisdom tooth that digs into that hole? Go see a dentist.