Antipodean:
How would I stop people calling a Patrick: Paddy, Pat, Rick?
I would like a boy to be just Patrick or is it just one of those things you have to deal with in life?
When you hear someone refer to him this way firmly say, "His name is Patrick, we are not using a nickname". Then smile.
Of course, that's only going to work until he can talk or goes to school. He may decide that he likes being called Pat or Rick (or Spiderman). My parents named me Paula Grace and I've gone by Gracie since 1st grade. I always hated Paula for some reason. It's still my legal name, but I don't use it. I use Grace for everything, even used it for my marriage vows.
Ultimately nicknames are up to him. So, if there's a nickname you don't like than don't use that name.