Some crackhead pressed his thumb in the centre of the back of my neck & since that I keep getting a spot there?

Some crackhead man told me he just his leg so could I walk him up the road to the shop & he started shouting at me saying love makes him sick and his ex wife died on a couch one morning.. anyway he started talking about conspiracys and said the government put chips in the back of people's necks and before I could react he put his thumb on the back of my neck and pressed it like a button.. I started to get annoyed coz I was trying to him him but I left it then he asked if I could help him in the shop and he started slapping my face and I told him I'd knock him out if he carried on then he said he's sorry he's drunk and I walked out (coz I know the shop owners and didn't want to have a fight in their shop) anyway I decided to leave it & a couple weeks later I noticed a spot there like a couple weeks later & it's literally like some curse that won't go away now... I'm considering putting some special acid on it to get rid of it but yeah... It's literally in the exact same place every time too... every time it goes away it comes back and it's been over a year now... anyone have any ideas??