Make matters worse by harping on about something (3,2,2)
I believe the answer is:
rub it in
(Other definitions for rub it in that I've seen before include "Unkindly emphasise" , "Harp on to someone about something of which he does not wish to be reminded" , "Remind or taunt someone about unpleasant fact" , "Continue to remind one of a mistake" , "Harp on something distasteful to person not wishing to be reminded of it" .)