My information comes from Jastrebarsko, Croatia microfilmed church record, film #1920523. I did not find a Petar Dimnjakovic born 1885 in these records. I found a Petar Dimnjakovic born May 23 1886 in Cabdin. There was a note that he died 1958 in Cabdin. Unless your Petar went back to Croatia, this must not be your Petar.
Check familysearch.org Just enter Dimnjakovic and see what info they have