"I have got an apple." means "I have an apple". ("got" is totally unnecessary).
("I got an apple" is sometimes incorrectly used to mean "I have an apple.")
"I got an apple." correctly means "I received an apple." - it is very general (it can mean "I bought an apple", "I stole an apple", "I picked an apple from the tree", "I was given an apple for my birthday" or any other means of starting to have an apple).